Put options -- financial instruments which allow investors to profit from the decline in value of stocks -- were purchased on the stocks of American Airlines and United Airlines in great volume in the week before the attack.
Two of the corporations most damaged by the attack were American Airlines (AMR), the operator of Flight 11 and Flight 77, and United Airlines (UAL).
The Bloomberg News reported that put options on the airlines just days before the attack surged to the phenomenal high of 285 times their average. The spikes in put options occurred on days that were uneventful for the airlines and their stock prices.
When the market reopened after the attack, United Airlines stock fell 42 percent from $30.82 to $17.50 per share, and American Airlines stock fell 39 percent, from $29.70 to $18.00 per share.
And then there are the financial services corporations:
Merrill Lynch and Morgan Stanley Morgan Stanley Dean Witter & Co. and Merrill Lynch & Co. were both headquartered in lower Manhattan at the time of the attack. Morgan Stanley occupied 22 floors of the North Tower and Merrill Lynch had headquarters near the Twin Towers. Morgan Stanley, which saw an average of 27 put options on its stock bought per day before September 6, saw 2,157 put options bought in the three trading days before the attack.
Merrill Lynch, which saw an average of 252 put options on its stock bought per day before September 5, saw 12,215 put options bought in the four trading days before the attack. Morgan Stanley's stock dropped 13% and Merrill Lynch's stock dropped 11.5% when the market reopened.