It can be. And it also places strain on the people around you too if the kid isn't settled and easy to travel with.

Not the kids fault, but last time I travelled, there was a couple travelling with a child that was crying, hysterically the entire trip. This was a 20 hour trip all up, from NZ to SA, crossing NZ to AU then to SA, and they were with us all the way. The kid was going for the entire thing - I watched the parents take turns to look after her, standing near the toilets. I feel sorry for them having to deal with that, and for the girl being that upset (presumably sore ears? dunno), but that would not have been fun for the people around them either.

I was always super wary of travelling with ours in case that happened. We were lucky that they just slept through all the flights, but it could have easily gone the other way. I would have felt pretty stink subjecting the surrounding 40+ people to a very upset child.