Well, lets look at this rationally. What are the arguments for forbidding law-abiding citizens with CCW/CWP (concealed weapon permits) from carrying on an airplane?
1. Depressurization/other functionality mishap.
This has been proven to be effectively mythical, at least from the cause of handgun bullets. If you're worried about it anyway, we can require low-penetration frangible rounds.
2. CCW gone crazy: the permit holder with the gun goes nuts. This is as much of a myth as depressurization due to handgun bullets. As mentioned before, crime statistics show that permit holders have such a low rate of violent crime it is virtually zero. In the unlikely chance that it did happen, an armed flight crew and maybe one or two other armed passengers would deal with it.
3. Terrorist/etc grabs CCW's gun. Well as I mentioned earlier, concealed carry means hidden. Properly concealed, you'll sit next to a CCW for hours and never realize he is armed in most cases. Without X-ray vision, determining who is armed, if anyone, is iffy.
Even if you did, taking a gun from an "educated CCW" is not at all like taking candy from a baby. Even if someone managed it, there would be the armed flight crew and perhaps other armed passengers to deal with. This is a non-issue.
4.. Crowded conditions
NOW, here is an intresting one. Yes, the conditions are crowded, and the risk to bystanders considerable.
However, let's consider the circumstances under which a rational armed citizen might use that weapon... terrorists, violent looney with a razor slashing people, hijackers...well, then again it is hard to tell the latter pair from the first one since 911. In short, it would be a desperate situation where everyone's lives were already in danger. Consider Flight 93.
The danger could be largely mitigated with good judgement and/or good marksmanship. I know plenty of CCW holders with both.
Now, come to think of it, crowded conditions applies to a lot of places, like malls, stores, restaurants. Do you oppose CCW in such places? Since we've narrowed the reasons to oppose CCW on a plane down to this one issue, the crowded conditions, let's address that issue as it relates to malls, stores, restaurants, buses, etc.
G.