I am so fortunate that the cries of other people's kids don't annoy me. It's not my hassle so it doesn't bother me at all. I can sit back and not even worry about it. No one would blame me for not lifting a finger to help with another parent's child is screaming so it means almost nothing to me.

I am in Maui on vacation right now and flew with 5 of my children here. One of them is only 5. She doesn't mind flying at all but I was reminded a few times how fortunate I am that flying has never bothered her each time a child several rows back screamed.
That would be stressful for a parent because you're stuck on an airplane with few options.