Spoiler Alert: Debt of Honor ends with a commercial airliner crashing into congress during the state of the union and killing the president and most of congress.
Osama Bin Laden planned for Sept 11, because he wanted to do it when Congress was in session.
Or Khalid could have read Clancy's follow-on book Executive Orders, at the beginning of which Captain Sato lands on Congress, catapulting Jack Ryan into the White House, ready to cope with a bio attack, among other things.
Or Khalid might simply have read the news. On 7 April 1994, a very nonfictional and profoundly disgruntled Auburn Calloway, just fired from Federal Express, came damn close to doing a 9/11 on his former employer's Memphis hub.
Heh. I was thinking the same thing last week, especially since there will need to be ways to 'cool off' in the hot Grecian climate.
Bojinka - the plan to crash even more planes into buildings, was discovered in 1995. This and other intel was the reason there was a no fly zone over Atlanta for the Olympics in 1996. Very interestingly, they were also looking for CROP DUSTERS.
There is still an armored Ayers crop duster from the State Department's Drug War air force missing. It can be ferryed thousands of miles by using the chemical tanks for fuel.