[5Madman2]

Reference Anthrax. Even militarized spoors would have a hard time surviving the fire to infect anyone. The Delivery systems for Bio agents use bursters that generate little heat, so as to not kill the bug as it's dispersed. I further don't think the hijackers had time or capability to disperse during the flyover.

[boris]

"Even militarized spoors"

Tanker planes raining liquid waste?

--Boris

[The Duke]

Oh, I'm not suggesting that the perps we know had any such opportunity, but rather that there may be others yet.