In the days before September 11, 2001, an unusual surge of put options — bets that a stock will fall — appeared on United Airlines and American Airlines. For two decades, that fact has fueled one of the more durable conspiracy theories about the attacks: that someone with foreknowledge profited as the towers fell. The story has staying power because the trades were real. What’s less discussed is what investigators actually found when they ran them down.
What the data showed
The volume was genuinely anomalous. In the trading days leading up to September 11, put activity on UAL spiked to roughly 90 times its daily average, and AMR saw similar disproportionate movement. The 9/11 Commission’s monograph on terrorist financing addressed this directly, and so did a separate SEC investigation. Both concluded the trades were not linked to al-Qaeda. The bulk of the UAL puts were traced to a single U.S.-based institutional investor with a bearish airline-sector newsletter strategy — the same investor had recommended the trade to subscribers days earlier. The AMR positions were tied to similar arms-length strategies. None of the buyers had any plausible terrorist connection, and the SEC was able to identify them within weeks.
Why the story persists anyway
A satisfying conspiracy needs three things: a real anomaly, an institutional explanation that sounds boring, and an authority figure people don’t trust. The airline puts story has all three. The trades did happen. The official explanation involves a sector newsletter, which is the most yawn-inducing answer imaginable. And the SEC, post-2008, is not a body most retail investors regard as a paragon of competence. So the rumor recycles every few years, often pinned to whichever financial figure is currently unpopular. Add the fact that most people don’t know what a put option is, and you have a perfect substrate for myth. The pattern matches almost every other “they knew” theory: a real signal, an unsexy resolution, and an audience primed to assume the resolution is a cover-up.
What it tells us about market signals
The episode is a useful case study in how markets do — and don’t — leak information. Genuinely informed trading on a major event would almost certainly involve more than two airline tickers; you’d expect movement in reinsurance, defense, and broad index puts as well. Researchers who looked for that wider footprint didn’t find one. That’s a meaningful negative result. Markets are good at aggregating diffuse information, but they’re also noisy enough that any sufficiently large sample will produce striking-looking anomalies in hindsight. The base rate of unusual options activity across thousands of stocks every week is non-trivial. Selection bias does the rest.
The bottom line
The pre-9/11 put options were real, investigated, and explained. That doesn’t mean every conspiracy claim collapses on inspection — sometimes regulators do miss things — but in this case the paper trail is unusually clear. The more interesting question isn’t whether someone profited. It’s why a fully resolved investigation continues to feel unresolved to so many people two decades later.
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