Okay, here is my bullshit thoughts on the subject, as promised (or threatened? )I've been known to be wrong. Would still like to read the post you referenced.
There is the problem of mixing theoretical and practical concerns. Yes, having many armed people on an airliner would provide a deterrent to a hijacking, but that isn't how it would work in reality.
Perhaps the strong dedication to training background of the individuals here have influenced some of the attitudes, you may be forgetting what the average skill level is out there in the "real world". Based on close observation of a host of firearms practitioners, there are few folks I would trust in an airliner cabin to be successful.
If you are going to allow anyone to carry a firearm on an aircraft, then you are counting on there always being a sufficient number of good guys armed onboard to handle the number of bad guys who now have the same access to going armed on an aircraft.
In today's world, that is not the case. Given the travel habits and the total number of LEOs in the country, there will be few sworn officers of any kind on board an airliner at any given time. LEOs simply make up a small percentage of air travelers (and I am one of them as I am a federal LEO and fly armed).
I would submit that allowing all LEOs to always carry would hardly move the numbers. The general public would have to provide most of the deterrence. However, when you look further at average passenger demographics, it would be far more likely that very few if any people would actually carry a firearm onboard a given flight. The current percentage of CCW holders versus the general population is very low. In other words, there are not many people in this country to provide an "armed passenger" corps if you will.
All this means that since we are depending upon a random deterrence by a small percentage of armed citizens, making it more likely that the bad guys would both outnumber, and out skill the typical CCW holder on any given flight.
That said, from where I sit, I would be all for allowing people to carry on an airliner, but only after a thorough background check, a difficult skills test, including recurrent training, some type of combatives to include force on force, and mindset training. That is way beyond the 2nd Amendment, but strong skills are required to be successful against an enemy that only fears failure. The background check would provide a way to reject obvious badguys without invoking the wrath of the ACLU, not to mention that no airline will allow an armed passenger program without it due to liability. Airlines don't even trust their own employees on this front.
Read the 911 report for further details on the motives and training of Al Qaeda, including the cockpit assaults. I don't buy the "we have nothing to lose" scenario argument- to win, an armed citizen is going to have to kill every single one of the hijacking team members.
What I suspect here is that many very skilled people would like to arm themselves on a commercial flight. That is natural and understandable, but the concept doesn't work when the probabilities involved allow for easy exploitation.
Due to liabilty, and a host of other sniveling management absolutions, no corporation is going to allow this to happen, unless the government forces them to do so. CEOs will simply pontificate about the travesty of it all in their best selling memoirs. They aren't accountable.
So don't hold your breath.
I gladly welcome armed people on any aircraft I am on, but I want to know that the person has demonstrated that he or she is a dedicated professional, well-versed in all facets of warriorcraft to include weapons retention, strong emphasis on mindset, combatives, and yes, familiarity with aircraft systems. There are some things that you don't want to shoot on a commercial jet. Pressurization is not a problem, but some other things are. The solution is to hit the target, every time, with an effective projectile that will not over-penetrate. That means annual practice round counts in the many thousands.
You all understand the ramifications of a marginally trained person jumping into a complex situation, and a passenger cabin is a particularly difficult tactical problem. One of the worst environments you can fight in. No cover, limited concealment, the whole thing is one giant fatal funnel. Bad news all around.
Until you establish high standards, don't even broach the subject of armed passengers on an airliner. As always, training is the answer.