Good point, and I'd assume that clearing a gun in a toilet stall would make enough gunny noises to attract unwanted attention. I would intent on throwing the weapon in a trash can _outside_ the bathroom, so the janitors would be expecting a heavy trash bag, as it wouldn't be filled with just paper towels.

If there's a plumbing access hatch in one of the toilet stalls, you could drop the weapon into the wall cavity, not to be seen for a long time.

This is purely academic, and I hope to never find myself in such a situation. I simply do not want my day ruined because one weapon caused a terminal lockdown.

BTW, if AQ is listening, idea for an attack: sneak knives airside and just start leaving them in random, "scary" locations, like in seat back pockets. Do this on several high-capacity aircraft scattered around the country, and sit back as you watch air travel grind to a screeching halt for something that poses zero real risk. Heck, you don't even have to call in bomb threats.