5. The non-stop talker. This passenger is either right in front of you, behind you (or worse yet) alongside you. And the yapping just goes on and on and on.
4. The space invader. This person overflows into your seat and maybe the seats and space of others to the point where you're positively scrunched thisclose to the window, the aisle, this person or some other person.
3. Children running wild. No one prepared them. No one told them. No one is willing to correct them.
2. Bad hygiene. Body order, bare feet, coughing, wheezing, foghorn nostrils, bad breath, dirty fingernails, unkept hair, body hair, sores and band-aids . . . . ugh!
1. The seat recliner. Let's recline the seat all the way back, right into your lap. There 'ya go!
And, to these we would add one other: Indulged and/or wailing kids. An epidemic of "designer children" and endlessly crying children. The worst!