"They should be out long enought to tie up, etc by crew with masks."
Why bother tying them up, "RW-1"... 10~15 minutes without oxygen and all the hijackers and passengers would probably be dead anyway. Passing out would be the
least of the hijackers worries.
And now we've discussed this and other hijack countermeasures in a public forum... the first thing a tuned-in hijacker is going to do is grab one of the onboard portable oxy kits <img src="rolleyes.gif" border="0">
Q.
P.S. And on the subject of gas.... Every now and then, pilots/engineers accidentally activate the emergency oxygen system (even though the switch is guarded). What's to stop them accidentally gassing themselves if there was a gas switch in the cockpit?