I think I've only seen one season 3 episode. I was getting tired of the "drunk of the week" focus in season 2. Seemed like there was more employee/behind-the-scenes emphasis in season 1 (love that Yolanda!), whereas in 2 the emphasis shifted more toward annoying/inebriated/loser travellers. I've also read internet rumors that some of these "passengers", especially at LAX, were actually 'ringers': Actors hired by the producers to act up.
I think the show has run it's course, and I hope there will not be a season 4 unless WN insists that it return to it's original slant of an inside look at airline operations rather than one snockered lowlife after another abusing the gate staff!