[Strategerist]

While very dangerous, they are not the terrorists' weapon of choice. Those would be manportable air defense systems (MANPADS) like Redeye (obsolete), Stinger, Blowpipe, SA-7/18, etc.

Actually MANPADS have a surpisingly small chance of taking down a large airliner.

[Belasarius]

I've always wondered about that. A 747, for instance, is a damn big airplane and, even if a Stinger managed to take out one engine, so what?

I don't know that commercial airliners have self-sealing tanks and other protections against sharpy, pointy, blowie-up things. Fuel going up might be problem.