Quality of PAX
I was waiting at the arrivals point of EMA to pick someone up from a Pisa flight a few years ago. As I pondered exactly when they may appear from behind the doors I noticed lots of people coming through dressed in athletic vests, gaudy shorts and pristine white trainers - clearly piling off the Costa Del Somewhere-or-ever flight. A little while later people started appearing with linen suits, hats, nice shoes etc so I guessed (correctly) that the Pisa flight was now piling out. Right on cue, the person I was waiting for appeared in amongst the beautiful people. I'm sure the same could have been spotted at any airport where the flights are not too frequent that you can't spot distinct groups of people appearing through arrivals.
That being said, there were a few tramps on a flight from Singapore I was on last month. And before someone says it, there is a difference between travelling in comfortable clothes for a long haul flight and looking like a street person.