^^What bqmassey said. Though we stand the chance of logic-ing ourselves to death. I have been thinking this as I watched this thread unfold. Everyone has a right to do as they are comfortable, and I am for each of us getting adequate training and doing what we think is right. As far as military SOP, the military has felt obligated to relegate to the lowest performing denominator in order to minimize NDs. Think "mil spec". Depending on what you are talking about, it could be great, or it could be the cheapest, "just good enough" solution. There's nothing wrong with it, we just have to see it for what it is.
I could easily say that if anyone is not competent to carry their sidearm in condition 1 (hammer action) or 0 (striker fired) safely in one specific scenario or another, I would not want them to carry around me in any scenario, period. 4 rules of gun safety. Flying or not. Burning car/plane/house or not. Stored or not. 4 simple rules. (Acknowledged: Burning wreckage and a dislodged body (thus the firearm, in holster, pointing somewhere unsafe) could cause a uncontrolled cook-off.)
Long guns are usually employed for known threats, and thus the norm would be to "carry" mag loaded, chamber empty, safety off, hammer down when outside of a known-threat area. Sidearms are either: a) backup.. for immediate deployment at failure of primary - condition 1 or 0. Or b) for immediate deployment against previously unknown threats. Condition 1 or 0.
If you need a sidearm for self-defense (on the ramp? During taxi?), it will all happen very fast, and half-seconds will be precious. If you take the time to find or load your weapon ready in a confined space, you either a) become a victim, or b) had time to avoid or evade (your best first options).
Also, if you haven't trained to safely and effectively deploy said weapon in the tiny, sight-line restricted confines of an airplane, that might be something you find time to do.... And when you do, use a blue-Gun or a safety barrel insert or something...
I can tell you that, were I a person to carry a sidearm, I would be absolute in my proficiency with clearing a weapon safely, and under no circumstances would that proficiency allow me to blindly declare that there is no increased risk when my weapon clears it's holster and exhibits an exposed trigger. I wouldn't clear in close proximity to others, and I wouldn't clear in public unless absolutely, absolutely necessary. If the risk of fire and a cook-off is enough to warrant that for you, then create a safe place to clear your weapon in the hangar, and do it in that spot every time. Please don't clear a weapon in a confined space... while your body is contorted in a weird shape.... not to mention the cost of repairs should you do what many, many have done while clearing their weapons (while not focused on the task at a hand).