Well, it is used in at least some of the things you mention. However different places can have varying methodologies which skews things and its effectiveness. For instance, US airports are particularly jackasses about it and overall shamefully ineffective (as of the last time I read about it anyways), their job desceiption might as well be to make everyone's socks dirtier at checkpoints.
Still, the thing is mainstream enough to have its own wikipedia page. I am not sure of what airplane events you are refering too though (if its within the US you can just google how ineffective US airport security is).
Well, if a person literally flips to the extent you suggest (from average joe to the joker) within a period hours then there really is nothing to stop that person (unless he doesn't own a gun and buying a gun takes more than a few hours). And to be fair, what I am suggesting does not necessarily involve checking literally every person (though I can't stress enough the issue would be whether this could work in this specific scenario which would have to be done by people who know more than me about profiling and guns). Even if this specifically does not work for this scenario, it means nothing in regards to other means of implementing stricter gun control.