Looks like this is true.
I just checked this
www.snopes.com. This is a very good site for verifying the truth behind these rumors.
"In the month prior to the 11 September 2001 attacks on the World Trade Center and the Pentagon, highly unusual trading activity Stocks involving American and United Airlines stock was noted by market analysts who at the time had no idea what to make of it. Wildly unusual discrepancies in the put and call ratio -- 25 to 100 times normal -- were observed in stock options of the two airlines. In one case, Bloomberg's Trade Book electronic trading system identified option volume in UAL (parent of United Airlines) on 16 August 2001 that was 36 times higher than usual. "
You can find the whole story at
www.snopes.com. Do a search on "put paid" (I could not figure out how to get a direct link).
I am sure that if they found any of the owners of these contracts (either American or otherwise) they would act appropriately.