There's more than one to look at it. The traders might have known something, but it wouldn't necessarily have been what actually happened. What were they trading in again?
A few entities bought 1000 times the normal volume of put options on Airline stocks in the days leading up to 9/11. This has been confirmed by reports and an insider named Max Kaiser who had contacts working in the towers telling him they were buying puts on American Airlines due to the possibility of planes hitting the towers. Put options are basically a contract to sell a stock at a particular price, so when the stock falls in value, you gain net profit.
Strangely enough, many of the options were not
exercised at the strike price. In other words, whomever bought many of those options did not take the money. I don't know what to make of it, but not exercising those options is ridiculous at any other time in history.
I've researched the hell out of this. There was no detrimental news regarding airline stocks in the days before 9/11, there was no major shocks to the crude market in the days before the attack to signal a decline in airline stocks, and there was no signs in technical analysis to explain why someone would take a huge position in those options. So to this day, this event looks extremely suspicious and makes absolutely no sense.
Unfortunately, it looks like someone had prior knowledge, which is scary because it means some of our leaders might have known as well.