What time were the flights scheduled to depart....before or after the 9/11 strikes here in the US....???
This sounds to me like they were MUSCLE who realized they were going on a suicide mission and got cold feet.
AFTER the WTC attacks by several hours apparently. The pilot was the one who got cold feet looking at the increased security at Heathrow, and left.
Most "jihadists" get cold feet and wind up doing something besides suicide. That's why such people have their hands tied to the steering wheels of car bombs...or why their handlers detonate their backpack bombs for them.
It also points to one of many weaknesses of Al Qaeda's decentralized cell structure; timing. The U.S. attacks were to be supported by the Al Qaeda suicide squads in Australia, Britain, and India...but they didn't know the precise details of the U.S. ops...so they were late enough to the party that they encountered tighter security in the UK, Australia, and India that had a hand in thwarting all of those attacks.