The September 11 Market Shock

Key Takeaways

• The market did not crash on September 11. It never opened. The New York Stock Exchange stayed closed for four trading sessions, September 11 through 14, the longest shutdown since the Great Depression, because its building and lower Manhattan's power and telecommunications lines were damaged, not because of anything wrong with a company, a bank or a price.
• The real emergency was in the plumbing, not the ticker. The Federal Reserve's Fedwire payments system saw the number of transfers fall by more than 40 percent and their value fall by a quarter on September 11 alone, because banks that normally fund outgoing payments with incoming ones grew afraid to send money without knowing what they would receive.
• The Fed answered with a liquidity flood of a size it had never deployed before. Discount-window lending, which typically ran under $1 billion outstanding, reached roughly $46 billion on September 12. Average weekly borrowing, near $143 million before the attacks, hit an all-time high of $11.8 billion that week.
• When trading resumed on September 17, the Dow fell 684.81 points, over 7 percent, the largest one-day point loss in its history at the time. The Nasdaq Composite fell 6.8 percent that day and did not stop falling until the following Friday.
• The theory that terrorists profited from advance knowledge through short selling and put options was investigated exhaustively by the SEC, the FBI and foreign regulators. The 9/11 Commission's report states plainly that every instance of unusual trading it examined had an innocuous explanation.

What Happened to the Stock Market on the Morning of September 11?

The New York Stock Exchange normally opens for trading at 9:30 a.m. Eastern time. American Airlines Flight 11 struck the World Trade Center's North Tower at 8:46:40 a.m., 43 minutes before the bell. The exchange, along with the American Stock Exchange nearby, had not traded a single share that day.

One market had already been open for hours: U.S. government securities, which begin trading early in the day. Billions of dollars in Treasury trades had been executed but not yet settled when the attacks began. The two banks that dominated clearing for that market, the Bank of New York and J.P. Morgan Chase, were both headquartered within blocks of the World Trade Center and had to evacuate to backup facilities, a logistical scramble that meant final reconciliation of trades already agreed to that morning was not completed for weeks.

The human cost fell hardest on firms with a floor presence in the towers themselves. Cantor Fitzgerald, a bond-trading firm whose New York offices sat near the top of the North Tower, lost 658 of its 960 New York employees, the single heaviest toll suffered by any market participant. The scale of that loss is part of why the closure that followed was not a policy choice made from a boardroom; entire trading desks and back-office teams no longer existed to staff a reopening.

Why Did the New York Stock Exchange Stay Closed for Four Trading Days?

The exchange's own building, several blocks from the World Trade Center, was damaged in the attacks, and power and telecommunications lines serving lower Manhattan were severed along with it. Temporary repairs were not completed until early the following week. Trading did not resume until Monday, September 17, a closure spanning Tuesday through Friday of that week, the longest the exchange had gone dark since the bank holiday of 1933.

The closure was not purely a matter of physical damage. The Nasdaq, an all-electronic dealer market with no trading floor to repair, stayed shut over the same four days rather than reopening on its own schedule. Its chief executive later described the joint decision as, in his words, "a textbook example of effective cooperation among the government, markets, and private industry." Reopening a fragmented market, with one venue trading and another dark, risked concentrating order flow in ways nobody had tested and that regulators judged riskier than a coordinated four-day pause.

The American Stock Exchange, whose own building was also affected, did not attempt an independent reopening either; its operations were temporarily relocated onto the floor of the NYSE once trading resumed, an accommodation the SEC authorized under its emergency powers.

What Broke First: Why Did the Payments System Nearly Seize Up?

Long before anyone was worried about where the Dow would open, the more urgent problem was whether banks could pay each other at all. Fedwire, the Federal Reserve's large-value payment system, is the circulatory system beneath every other market: banks use it to settle trades, meet reserve requirements and move money on behalf of customers, and they routinely fund an outgoing payment with an incoming one received earlier the same day. On September 11, the number of Fedwire payments fell by more than 40 percent and their total value fell by a quarter, because some banks, including institutions with no direct damage of their own, could not connect their backup systems to the network at all.

A Federal Reserve Bank of New York study of the episode measured the effect precisely: the end-of-day flow of funds over Fedwire normally runs near $10 billion per minute; on September 11 it fell below $2 billion per minute. The timing of payments also became erratic, with the typical spread between when a bank expected a payment and when it arrived nearly doubling, to about four hours, and payments arriving roughly two hours late on average.

The mechanism the researchers identified is a coordination failure, not a solvency one. Once banks could not be sure an expected payment would arrive on schedule, they held back their own outgoing payments as a precaution, which meant the banks waiting on them also fell short, and so on. No bank in this chain was insolvent. Each was simply unwilling to send money it might not be able to replace. That distinction, uncertainty about liquidity rather than a question about anyone's underlying balance sheet, is what determined which tool the Fed reached for first.

A second, unrelated breakdown compounded the problem. With the Federal Aviation Administration grounding all U.S. air traffic, the Fed's own system for physically flying paper checks between its regional districts stopped functioning. Rather than let that hold up payments to receiving banks, the Fed chose to keep crediting banks as usual for checks they deposited, even while it could not yet collect from the banks that had issued them. That decision widened "float," the gap between what the Fed pays out and what it has collected, from an average of $766 million a day over the first eight months of 2001 to $28 billion in the days that followed.

How Much Liquidity Did the Federal Reserve Actually Inject, and How Fast?

The Fed's first move was simply to say it was still functioning. At 9:44 a.m., less than an hour after the first plane hit, it sent a message over Fedwire itself stating the System was "fully operational at this time and will remain open until an orderly closing can be achieved." A short public statement followed that morning: "The Federal Reserve System is open and operating. The discount window is available to meet liquidity needs."

That last sentence was not boilerplate. Discount-window borrowing, the emergency loans the Fed makes directly to banks against collateral, had generally run under $1 billion outstanding in the weeks before the attacks. It spiked to roughly $46 billion on September 12, more than two hundred times the average daily lending of the prior month. Measured a different way, average weekly discount borrowing during 2001 before the attacks had been $143 million; during the week of the attack it ballooned to an all-time high of $11.8 billion, before dropping back to the $1 billion to $1.5 billion range within two weeks and returning to normal shortly after.

Alongside the discount window, the trading desk at the Federal Reserve Bank of New York, working from a backup facility in New Jersey, ran daily open-market operations from September 12 through September 17, meeting every dollar of demand from its counterparties at the target federal funds rate rather than rationing it. The Fed also waived the penalty fees it normally charges banks that run temporary overdrafts on their Fed accounts; such overdrafts ran about a third higher than usual over the ten days following the attacks. For foreign banks that needed dollars but held little eligible U.S. collateral, the Fed arranged new temporary swap lines with the European Central Bank and the Bank of England and expanded an existing one with the Bank of Canada, letting those central banks swap their own currency for dollars and re-lend the dollars at home.

Who Was Actually Running the Federal Reserve That Day?

Almost the entire Board of Governors was out of reach. Six of the Fed's seven governors were traveling on September 11. Chairman Alan Greenspan was on a commercial flight home from a meeting of central bankers in Basel, Switzerland; when the FAA grounded U.S. airspace, his plane turned back to Zurich. New York Fed President William McDonough had attended the same Basel meetings and could not reach Washington either. The one governor in the building was Vice Chair Roger Ferguson, and for most of that day, working the phones with Reserve Bank presidents and System staff, he effectively was the decision-maker.

The most consequential decision he made was one he blocked rather than one he issued. Some officials elsewhere in government floated the idea of a nationwide bank holiday, closing the entire banking system to give recovery efforts room to work. Ferguson argued against it, on the reasoning that closing banks would make ordinary depositors unsure whether they could get their money and risked manufacturing the very panic a holiday was meant to prevent. No bank holiday was declared.

Where the wires themselves would not cooperate, the fix was manual. Bankers who could not connect their backup systems to Fedwire called New York Fed staff directly, often on personal cell phones, and read off the payments their institutions needed to make; Fed staff then entered those instructions into the system by hand. It is not the kind of detail that shows up in a market index, but it is a fair description of how close the payments system came to a full stop, and of how much of the initial response depended on individual judgment rather than a pre-written playbook.

What Did the Federal Reserve Do to Interest Rates?

The Federal Open Market Committee held an unscheduled meeting and cut its target for the federal funds rate by half a percentage point, to 3.00 percent, announced before trading resumed on the morning of September 17. The accompanying statement reiterated that the Fed would keep supplying ample liquidity to counter what it called extraordinary strains in financial markets.

The Fed pushed so much liquidity into the banking system that the rate banks actually charged each other overnight fell well below that new 3 percent target. In the week following the attacks, the effective federal funds rate averaged just 1.2 percent on the two days when liquidity concerns were most acute, a deliberate undershoot the Fed tolerated because it confirmed the liquidity was reaching the market rather than sitting unused.

It is worth separating this cut from the broader run of easing that followed it. The September 17 move was a targeted, event-driven response, timed to the market's reopening. The Fed kept cutting through the rest of 2001 as part of a longer campaign against a slowing economy that had begun months earlier, ending the year with its target at 1.75 percent, the lowest level in 40 years at that point. Reading the full year's rate cuts as a reaction to September 11 overstates the attacks' role in that broader campaign, even though the September 17 cut itself was unambiguously a response to it.

How Did the Treasury Market Reopen Before the Stock Market Did?

The U.S. Treasury's own daily interest-rate data shows the government securities market functioning again days before the New York Stock Exchange reopened. No rates were published for September 11 or 12; quotes resume on September 13, four days ahead of equities, even though final settlement of trades from the morning of the attack was still being sorted out at the two damaged clearing banks.

The move in yields is a clean illustration of where the flight to safety actually went. The three-month Treasury bill yield, which stood at 3.26 percent on September 10, fell to 2.74 percent by September 13, 2.59 percent on the reopening day, and 2.19 percent by September 19, a decline of more than a full percentage point in about a week as investors piled into the shortest, most liquid instrument available and priced in the coming rate cut. The ten-year Treasury yield moved far less over the same stretch, from 4.84 percent on September 10 to 4.63 percent on September 17, which tells you the rush was concentrated in cash-like safety, not a broad-based flight into long-duration bonds.

Yields are constant-maturity rates from the Federal Reserve Board's daily interest rate release, retrieved via the Federal Reserve Bank of St. Louis's FRED database.

What Emergency Powers Did the SEC Use When Trading Resumed?

The Securities and Exchange Commission has statutory authority to alter its own rules for up to ten business days at a time when a "major market disturbance" threatens fair and orderly trading, and it invoked that authority repeatedly in the days around the reopening.

• Buyback rules relaxed. The SEC eased Rule 10b-18's timing and volume limits on company stock repurchases, so issuers could support their own shares without stepping outside the rule's normal safe harbor from manipulation liability.
• Insider "short-swing" liability narrowed. Purchases, though not sales, made by corporate insiders during the emergency period were exempted from Section 16(b)'s usual six-month profit-matching rule, while insider-trading and antifraud rules stayed fully in force.
• Blackout-period breaches excused. The Commission stated that a company's noncompliance with its own internal trading blackout policy during the emergency window would not, by itself, be treated as evidence of a securities-law violation.
• Airlines and insurers fast-tracked. Issuers in the two hardest-hit industries kept their shelf-registration eligibility even if their market float had since dropped below the usual threshold, and the SEC committed to reviewing their filings within five business days.
• Amex relocated onto the NYSE floor as an emergency accommodation while its own facilities were unusable.

One request the SEC turned down is as telling as the ones it granted. Parts of the securities industry asked the Commission to ban short selling outright. Chairman Harvey Pitt refused, noting that short selling had never been banned in U.S. markets, not even after the attack on Pearl Harbor, and that it served a legitimate liquidity function the market needed more, not less, in a period of stress.

What Happened When the Dow and Nasdaq Reopened on September 17?

Volume, not chaos, was the story of the day mechanically. More than 4 billion shares traded across the NYSE, Amex and Nasdaq combined, bordering on the most active trading day in history at that point, and the more than 2.3 billion shares that changed hands on the NYSE alone were the heaviest single day in that exchange's history to that point. Regulators framed the goal in those same terms beforehand. Days before the reopening, the SEC stated it had "full confidence that the attacks of September 11, 2001, will have little lasting market impact" and that it would use every available means "to facilitate the reopening of fair and orderly markets," not to engineer any particular price outcome. By that standard, measured in volume traded rather than in which direction prices moved, the reopening held.

Prices, on the other hand, moved sharply in one direction. The Dow Jones Industrial Average closed down 684.81 points, a fall of just over 7 percent, the largest single-day point loss in the average's history at that time, exceeding in absolute points the 508-point drop of Black Monday, October 19, 1987 (a much larger one-day percentage move at the time it happened, since the index itself was far smaller in 1987). The Nasdaq Composite, which had closed at 1,695.38 on September 10, its last session before the attacks, fell to 1,579.55 on September 17, a 6.8 percent decline in a single session even after four full trading days for the news to be absorbed.

How Far Did Stocks Fall, and How Long Did the Selloff Last?

The reopening day was not the bottom. The Dow fell further on September 19, down another 144 points, or 1.6 percent, and continued to incur losses across that week. The Nasdaq Composite's daily closes, which are fully documented in the Federal Reserve's own data series, show a cleaner picture: the index fell in every one of the five sessions after reopening, without a single up day, bottoming at 1,423.19 on Friday, September 21, a cumulative loss of just over 16 percent from its September 10 close.

Nasdaq Composite Index daily closes, Federal Reserve Bank of St. Louis (FRED series NASDAQCOM).

Notice what changed on September 24: the first positive session came the following Monday, six trading days after reopening, not immediately. A selloff of this size did not resolve itself in a single relief rally; it took the better part of a week to find a floor and another full week beyond that to begin a sustained climb back.

Which Assets Moved the Other Way, and Why?

The clearest verified evidence of where money moved defensively is in short-term interest rates rather than in any single winning stock. The three-month Treasury bill yield's drop of more than a full percentage point in about a week, detailed above, is a direct read of investors and institutions crowding into the shortest, safest instrument available while also anticipating the Fed's rate cut. That is the textbook definition of a flight to quality: not necessarily buying an asset that goes up, but paying a premium (accepting a lower yield) for the certainty of getting cash back on time.

On the equity side, the clearest signal is regulatory rather than a specific verified index number: the SEC's own emergency relief for shelf registrations and capital access was targeted specifically at the airline and insurance industries, which the Commission itself described as "particularly damaged" by the attacks. Airlines faced a direct hit to a core assumption of their business, that people would keep flying, at the same time insurers faced the largest insured-loss event in the industry's history to that point. That the SEC built bespoke relief around exactly those two sectors is itself evidence of where the market's stress concentrated, even without a specific verified percentage decline to attach to any one company's stock.

Did Terrorists Actually Profit From Insider Trading Before the Attacks?

This question deserves a direct answer because the theory that al Qaeda financed or profited from the attacks through pre-knowledge stock trades spread quickly and persisted for years. It has a specific origin: put option volume, contracts that pay off when a stock falls, spiked in UAL Corp, United Airlines' parent, on September 6, and in AMR Corp, American Airlines' parent, on September 10. On its face, that pattern looked exactly like someone betting on an attack before it happened, and by 2002 it was being taken seriously enough that the SEC was, in a contemporary legal journal's words, devoting "substantial resources" to the question.

The 9/11 Commission's later investigation, drawing on the SEC's and FBI's work together with cooperating foreign governments, closed the question. Its report states the finding without hedging: "Some unusual trading did in fact occur, but each such trade proved to have an innocuous explanation." A single U.S.-based institutional investor with no connection to al Qaeda bought 95 percent of the September 6 UAL puts as part of a broader trading strategy that also included buying 115,000 shares of American Airlines stock on September 10, a purchase, not a bet against the company. Much of the seemingly suspicious American Airlines trading on September 10 traced to a specific U.S. options-trading newsletter, faxed to its subscribers the day before, that had recommended exactly those trades for reasons unrelated to any attack.

The lesson is not that nobody should ever look at unusual trading patterns around a shock. It is that an unusual pattern is a lead, not a conclusion, and that this particular lead was chased by two federal agencies and multiple foreign governments before being closed out. A theory that fits the facts on the surface, and this one did, is not the same thing as a theory that survives investigation.

How Long Did It Actually Take the Market to Recover?

Different measures recovered on different clocks, and conflating them is the single most common way this event gets misremembered. On the Nasdaq Composite's own daily closes, the index did not close above its September 10, pre-attack level again until October 11, 2001, when it closed at 1,701.47. That is roughly a month, and specifically nineteen trading sessions after the reopening.

The S&P 500 followed a similar path on a slightly different clock. According to the federal government's own Economic Report of the President for 2002, the S&P 500 "had returned to its pre-September 11 level by mid-October" and finished the year near 1,150, up 19 percent from its post-attack low, with the Dow and the broader Wilshire 5000 rising in a similar pattern.

The economic recovery is a separate story from the market's. The National Bureau of Economic Research, the official arbiter of U.S. recession dates, marks the 2001 recession as running from March 2001 to November 2001, an eight-month contraction. That means the recession had already been under way for roughly six months before the attacks happened, and it officially ended the same month the equity market's confidence was stabilizing. Reading the market's V-shaped price recovery as proof the economy escaped the attacks unscathed, or reading the recession as something September 11 started from nothing, are both oversimplifications the dates themselves do not support.

What Warning Signs Existed Beforehand, and What Didn't?

Readers of other case studies in this series are used to a build-up phase: rising leverage, a funding mismatch, a valuation that only worked if a favorable condition held. This event does not have one, and pretending otherwise would be dishonest. There was no financial precursor. No bank was overextended in a way that mattered to what happened next; no currency peg or funding structure gave way. The vulnerability that mattered here was physical and organizational, not financial: critical market infrastructure, the exchange building, the two dominant government-securities clearing banks, telecommunications trunk lines, was concentrated in a few square blocks of lower Manhattan, and nobody had planned for that concentration to be destroyed on a single morning.

There was, separately, a documented intelligence warning that had nothing to do with markets. On August 6, 2001, President George W. Bush received a Presidential Daily Brief titled "Bin Ladin Determined to Strike in US," the thirty-sixth item that year to reference bin Laden or al Qaeda and the first to focus specifically on a domestic attack. It described a pattern of threats and past statements rather than a specific date, place or method, and the 9/11 Commission's own account makes clear it did not amount to actionable, specific warning of the September 11 plot. That is worth stating plainly for what it is: a genuine intelligence signal about the broader threat, not a market signal, and not one that told anyone what to do with a portfolio.

What Did Regulators Change About Market Infrastructure Afterward?

The most durable policy legacy of this event is not a rate decision; it is a rewrite of how the financial system thinks about where its critical infrastructure physically sits. In April 2003, the Federal Reserve Board, the Office of the Comptroller of the Currency and the SEC jointly published an Interagency Paper on Sound Practices to Strengthen the Resilience of the U.S. Financial System, built explicitly around "the post-September 11 risk environment." Its central finding was that back-up sites for core clearing and settlement organizations were often clustered close to their primary sites, sometimes sharing the same power grid, telecommunications trunk or transportation links, which meant a single regional disruption could take out both a firm's main operation and its supposed fallback at once, exactly what nearly happened to Bank of New York and J.P. Morgan Chase.

The paper stopped short of mandating a specific distance between primary and backup sites, but it pushed hard in that direction, calling on core clearing and settlement organizations to substantially achieve geographically dispersed, functionally independent backup capacity by the end of 2004, and giving other systemically important firms roughly three years from the paper's publication to do the same. The underlying logic, that a firm's disaster-recovery plan is worthless if its backup facility can be knocked out by the identical event as its primary one, is the direct policy descendant of what happened to Fedwire and the Treasury clearing banks in September 2001.

Readers should treat the specific implementation deadlines above as history rather than current rule: they were 2003-era targets for a 2004-2006 build-out that has long since happened, and operational-resilience standards for exchanges and clearing agencies have continued to evolve since, including through the SEC's later Regulation Systems Compliance and Integrity. Anyone relying on current resilience or business-continuity requirements for a specific institution should check that institution's present-day regulatory obligations directly rather than this page.

Common Myths About the September 11 Market Shock

"The stock market crashed on September 11." It did not, because it never opened. Every headline about a "9/11 crash" describes what happened on September 17 and the days after, when a market that had been closed for four sessions absorbed a week's worth of repricing in a handful of trading days. The distinction matters because it means the event was, mechanically, a delayed reopening followed by a sharp but ordinary-looking selloff, not a market that failed to function while open.

"Terrorists made a fortune shorting the market before the attacks." This is the most persistent myth associated with the event, and the 9/11 Commission investigated it to closure. Every specific instance of unusual pre-attack trading examined by the SEC, the FBI and cooperating foreign governments had an ordinary, unrelated explanation, documented above. No verified link between the attacks and profitable trading was ever found.

"The Fed couldn't respond because Alan Greenspan was stuck on a plane." The Fed's chairman was indeed unreachable for most of the day, along with five of the six other governors. That did not stop the response; Vice Chair Roger Ferguson, working with Reserve Bank presidents and staff, issued the "open and operating" statement within an hour, blocked a proposed bank holiday, and had the discount window and open-market operations running within the day. The institution's ability to act did not depend on one person being in the building.

"Wall Street stayed closed because the exchange building was destroyed." The NYSE building was damaged, not destroyed, and it was repaired within a week. What actually forced and extended the closure was the loss of power and telecommunications across lower Manhattan, the relocation of the government securities market's main clearing banks, and a deliberate, coordinated decision by the NYSE, Nasdaq and Amex to reopen together rather than in staggered fashion.

"September 11 caused the 2001 recession." The National Bureau of Economic Research's own dating puts the start of that recession in March 2001, six months before the attacks. The attacks worsened and likely helped compress an existing downturn, most visibly through the hit to air travel, tourism and business investment, but they did not create a recession that was not already under way.

What a Reader Can Actually Carry Forward

It is tempting to file this case away as a one-of-a-kind tragedy with no repeatable lesson for an investor. Some of it genuinely is one of a kind. But the parts of the story about how markets are actually built have direct, current relevance.

What generalizes

• Concentration risk is not only a credit or leverage story. The two banks that dominated clearing for the entire U.S. government securities market both sat within blocks of the World Trade Center. Neither bank was undercapitalized or mismanaged; the risk was purely geographic, and it took down a market function that had nothing to do with either bank's balance sheet. See clearing, settlement and brokerage mechanics for how that plumbing works today.
• A functioning lender of last resort can turn a liquidity problem back into a non-event, even when no institution involved is actually insolvent. The Fed's discount-window and open-market response addressed a coordination failure among fundamentally sound banks. Recognizing that distinction, illiquidity versus insolvency, is the single most useful analytical habit this case teaches. See stress testing and scenario analysis for how to plan around scenarios like it.
• "Unusual trading" headlines need verification, not belief. The put-option pattern before September 11 looked exactly like foreknowledge and turned out to be coincidence, twice over, once for United and once for American. Whenever a similarly clean-looking story shows up around a later event, the correct instinct is to ask who investigated it and what they found, not to accept the pattern on its face.
• A market shock does not have to originate in finance. Every other event in this series began with a credit, currency or valuation problem that could, in principle, have been foreseen by a sufficiently careful analyst. This one began with an act of terrorism that no market model was built to price. Scenario planning that only stress-tests financial variables will always miss shocks like this one.

What does not generalize

• The four-day market closure itself. It was possible, and coordinated across three exchanges, because 2001-era market infrastructure still had specific physical chokepoints that have since been deliberately redesigned away, in large part because of this event.
• The specific menu of SEC emergency relief. Buyback-rule relaxation and the Section 16(b) exemption were one-time uses of a ten-business-day emergency authority triggered by a declared "major market disturbance." They are not a standing playbook available to an ordinary investor or company in any period of stress.

The question worth asking now

Not whether a terrorist attack could shut down a market again, which is a question for security planners rather than investors, but a narrower and more useful one: for any service you depend on for custody, clearing or execution, do you know whether its stated backup facility is genuinely independent, in a different power grid and a different metropolitan area, or is it close enough to the primary site that the same regional event could take out both? For most retail investors that question is answered by the broker's and custodian's own regulatory obligations, which is exactly why the resilience rules described above exist. For anyone running a business that depends on a single financial counterparty or a single data connection, it is worth asking directly.

Related Reading

• Black Monday, 1987, the previous record holder for a single-day point loss, and a useful contrast in how much larger the percentage move was relative to a much smaller index.
• The 2020 COVID crash, for a shock that also arrived with no financial precursor, but where the exchange itself stayed open throughout, relying on circuit breakers rather than a multi-day closure.
• The 2008 financial crisis, for a contrasting case where the vulnerability was leverage and funding rather than physical infrastructure, and where the Fed's liquidity tools had to be paired with solvency support that this episode never required.
• Trading sessions, halts and volatility controls, for how markets decide to pause or reopen trading today.
• All Swoopr market history case studies.

References

Every figure on this page was verified against the following sources, each retrieved on 26 August 2026:

• Federal Reserve History: The Federal Reserve's Response to the September 11 Terrorist Attacks: the exchange's closure and reopening dates, the Fedwire payment and value declines, the float figures, the discount-window peak of roughly $46 billion on September 12, the overdraft and swap-line details, the FOMC's 50 basis point cut, the Board of Governors' unavailability and Vice Chair Ferguson's role, and the Cantor Fitzgerald casualty figures.
• Federal Reserve Bank of New York: Liquidity Effects of the Events of September 11, 2001 (McAndrews and Potter, Economic Policy Review, November 2002): the per-minute Fedwire flow figures, the payment-timing variability and delay statistics, and the payments-coordination mechanism.
• Council of Economic Advisers: Economic Report of the President, 2002, pp. 31 to 32 and 48 to 49: the S&P 500's recovery to its pre-attack level by mid-October and its 19 percent rise from the post-attack low, the average weekly discount-borrowing figures before and during the attack week, the FOMC's rate action, the effective federal funds rate averaging 1.2 percent, and the year-end 2001 federal funds target of 1.75 percent.
• International Lawyer: The SEC and the Securities Industry Respond to September 11 (Marc I. Steinberg, 36 Int'l Law. 131, 2002): the four-day closure description, the reopening-day trading volumes, the Dow's 684-point and later 144-point declines, the DJIA's approximate September 10 and year-end 2001 levels, and every SEC emergency-order action described, including the Rule 10b-18, Section 16(b), blackout-period, Form S-3 and short-selling items.
• National Commission on Terrorist Attacks Upon the United States: The 9/11 Commission Report: the timeline of the attacks including the 8:46:40 a.m. impact time, the August 6, 2001 Presidential Daily Brief, and the finding, in the report's own notes, that every instance of unusual pre-attack trading had an innocuous explanation.
• Federal Reserve, Office of the Comptroller of the Currency and Securities and Exchange Commission: Interagency Paper on Sound Practices to Strengthen the Resilience of the U.S. Financial System (April 2003): the post-September 11 backup-site concentration finding and the 2004 to 2006 implementation targets.
• Federal Reserve Bank of St. Louis: Nasdaq Composite Index (FRED series NASDAQCOM): every Nasdaq daily close cited on this page, including the September 10 pre-attack close, each reopening-week close, and the October 11 recovery close.
• Federal Reserve Bank of St. Louis: 10-Year Treasury Constant Maturity Rate (FRED series DGS10) and 3-Month Treasury Bill Secondary Market Rate (FRED series DGS3MO): every Treasury yield in the table above and the date trading resumed.
• National Bureau of Economic Research: US Business Cycle Expansions and Contractions: the March 2001 to November 2001 dating of the 2001 recession.

Rules that can change, and when this page was checked. The Interagency Paper's 2004 and roughly 2006 implementation targets for geographically dispersed backup facilities are historical benchmarks for a build-out that has long since happened, not a current standard; operational-resilience requirements for exchanges and clearing agencies have been revised more than once since, including through the SEC's Regulation Systems Compliance and Integrity. Market-wide trading-halt and circuit-breaker mechanics have also been substantially rewritten since 2001 and should be checked against current SEC and exchange rules directly rather than against anything on this page. Last checked on 26 August 2026.

Figures deliberately not stated. No weekly point or percentage total is given for the Dow Jones Industrial Average across the September 17 to 21 reopening week, because the Dow is a licensed, proprietary index not carried in full historical form by any primary source consulted this session; only the two individually sourced daily moves above are published. No specific percentage decline is attached to any individual airline or insurance company's stock. No figure is given for the total insured losses from the attacks, because no verified primary source supplied a reconciled figure in a form that could be quoted safely on this page.

Method note: all Nasdaq Composite and Treasury yield figures were retrieved directly from the Federal Reserve Bank of St. Louis's FRED database this session and are original calculations by Swoopr Investment from that underlying series, not restatements of a percentage reported elsewhere. Dollar figures for discount-window and float activity are quoted as reported in the Federal Reserve's own historical essay and the Economic Report of the President, and are presented separately where the two sources describe different measurement periods (a single-day peak versus a weekly average) rather than reconciled into one number.

This is educational content about a historical episode. It is not investment advice, it is not a forecast, and nothing here should be read as a claim about the current resilience, security or business-continuity posture of any exchange, bank or regulator named on this page.

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