You’re clearly pretty thoughtful about a lot of stuff related to this issue, and you clearly have a lot of experience as someone who works in the industry.
For that reason, i find it quite stunning that someone who works in the industry would actually make this claim. The likelihood of “criminals…hiding amongst the passengers” is far lower than it was before 9/11, precisely because of all the draconian security measures they have put in place since then.
Passengers are subject to more rigorous surveillance in their daily lives by a state security system that tends to err on the side of caution and often ends up placing the wrong people on no-fly lists. Once you’ve got your ticket, the physical screening procedures at the airport, combined with much stricter (and often asinine) rules about what you can carry with you, mean that even if a criminal does manage to get on the plane, he or she is not likely to be in possession of anything that can do very much damage at all.
And, finally, perhaps the biggest change made by 9/11 is that even if a criminal does manage to get onto a plane and try something, the very nature of the 9/11 attacks changed forever the consequences of an attempt to hijack or otherwise interfere with a plane in flight. In the 1970s, when hijacking was FAR more common than it is today, passengers and crew tended to follow the hijackers’ instructions because the general assumption was that cooperation was the course of action most likely to lead to a safe and peaceful outcome.
Since 9/11, though, that calculation is out the window. Any effort to take over a plane now will be met with massive resistance, because most people will understand—or, at the very least, believe—that they have nothing to lose by taking on the criminals. If anything is going to happen to a plane now, it will be because a passenger manages to sneak something really major like a bomb or a poison or something into his or her checked or carry-on baggage, and if a passenger does manage to do that, you can be sure that they won’t advertise their presence by making unauthorized trips to the bathroom or getting belligerent with the cabin crew.
Quite frankly, about the last thing that i ever think about when i fly these days is the possibility of terrorism; i’m far more likely to be made miserable by airlines that keep decreasing the seat pitch in their airplanes, understaffed TSA security lines, gate staff who refuse to make timely announcements or provide information about late aircraft or schedule changes, cabin crew who act like junior Mussolini, and passengers who can’t figure out the basic etiquette of getting their fucking luggage into the overhead bin and finding their seat within a reasonable amount of time. If the sometimes overbearing and plain assholish behavior of some cabin crew is the result of a fear of criminals on board, then those people need to get a fucking grip.