Toddlers can be even worse, and flying with several children can be the worst nightmare of it all.  I avoid flying as much as possible (though it has become a bit better as they are elder).

Buying really expensive tickets because of course everyone is flying home to grandma' just in the yule school holidays, and of course just before leaving from home, one of the children all of a sudden has changed his mind and decided that he absolutely not want to go to see grandma, the other child just decides that it's time to start packing, he can't leave home without all the toys, etc.

I think some of our worst nightmares was with the eldest, when he was the only one, and after he had gotten big enough to walk and even run.  Yes, he would run.  Through the security control, with a rucksack on his back and detectors beeping, and he continued running away from us, security officers not bothering at all with him - while we couldn't run after, of course we needed both to take off the shoes and belts and show everything in our rucksacks.  (This was in Russia after the Beslan affair, with tightened security regime).

Another time, on our way into China, he once again did the same and ran through the passport control and away from us!  And of course we couldn't follow after him without first getting our visas checked and stamped.

In 2004 we were frequently flying between St.Petersburg and Beijing, it was a flight leg that started off very nicely but gradually got worse and worse. Those old Soviet airplanes were equipped with collapsable baby beds at the front row of seats!  The route was flown by a medium-range airplane, so it touched down in Novosibirsk to load up more fuel and food.  Our son was sleeping very nicely there.  In the beginning we were allowed to let him sleep both under takeoff and landing, we were allowed to stay behind in the airplane while everyone else were pushed out of the airplane and into the duty-free shop for "security reasons" while the fuel were being tanked, but gradually the rules were tightened more and more, we couldn't use the bed under takeoff and landing, we had to go out of the airplane during our landing, and eventually we were not allowed to use the beds at all (the serving was also quite nice in the start, especially the food they picked up in Novosibirsk, I think that's probably the most authentic Russian snack I've ever had - but the last time we flew there was a complete and total ban on any alcoholic drinks onboard and they landed in Novosibirsk just to fill fuel and not to load any more food)

(Our son also ran away from us at the Tiananmen square, because someone was selling ice cream there - took us more than an hour to find him again).