Many years ago, you used to be able to walk into an airport, go up to the gate, and even board the plane without going through any kind of security check at all. You didn't even need a ticket. People greeted travelers as they were getting off the plane, and they could see people off at the gate. It wasn't unheard of for people without tickets to actually go on the plane to see people off - as long as they left before the door closed. Nobody thought much about danger from passengers in air travel.
Except, of course, for the cigarette smoke. People could actually smoke on airplanes. Eventually planes had designated smoking and non-smoking sections - but if you were within 3 rows of smoking, you were in smoking.
Of course both of these things changed. Security was first. I recall a trip to the airport when they had recently added a security station you had to go through to get to the gate (anyone could go to the gate, though). There was a big sign saying what you couldn't carry, along with a warning that all comments about weapons, hijacking, and the like would be taken very seriously.
One member of our group thought that was funny and (as a joke) said he'd better take his gun back to the car. The security person looked at him real hard and asked if he really wanted to say that. The correct response ("No, sir!") was given - the point was made and I don't recall other jokes being made about airplane safety at airports or on airplanes.
Some years later they gave up the farce that a small sign stuck on a headrest would magically keep the smoke away from the non-smoking section and made all US flights non-smoking. They make announcements about that before every flight, and apparently it's a federal offense to tamper with or disable the smoke detectors in airplane lavatories.
So, two rules that have been in effect for years - don't smoke on planes, and don't make comments (even in jest) that could sound like threats to airline safety.
Apparently not everyone got the memo. According to the news, a Qatari diplomat on a trip to Denver used the airplane restroom for a smoke break. When people became concerned about the amount of time he had spent in the lavatory, he is alleged to have made a reference to lighting his shoes.
Naturally the nice air marshals sat with him the rest of the flight to keep him company, and made sure he had an escort when they landed (along with some shiny steel bracelets). The FBI spent quite some time discussing this matter with both the diplomat and with the other passengers.
The diplomat did not pose an actual threat and is the beneficiary of diplomatic immunity - which means this will never go to trial. While many were inconvenienced, nobody was hurt.
Assuming the news stories are correct, I don't know if he was simply clueless and self-absorbed or an incredible jerk.