You really expect that there are enough people out there of Delta Force/SEAL caliber that are going to take a job for any amount of money where they fly around on airplanes all day. TALK ABOUT MIND-NUMBING WORK and low JOB SATISFACTION.
I say, make sure that either the PILOT or the CO-PILOT is armed, they've got to be there anyway. And, once the bad guys know they have guns, there will be NO MORE HIJACKINGS. So, it won't really matter if the pilots can actually shoot accurately (I think they can) anyway.
It's called a deterrent.
And this guy only needs to be good at one. A much easier task.
But you're once again applying rational deterrence theory to a bunch of crazies. I want someone there who can cap the SOB with a double-tap, for real, no foolin', because a "DETERRENT" only works against people as sane as me and thee.