For that Quito flight the crew I believe would have to be in the air by around 2 so they won't have to overnight the crew in Quito, for an EWR - HKG. The crew would have to be in the air by I believe 6:30 or so before we would be pulled off and replaced with another crew. Now if we arrived in a city late and were scheduled to work a flight out the next morning the flight would be delayed for crew rest issues. Example a layover is scheduled to be 8:45, but the inbound flight arrived 1 hour late, so the next flight they work would be delayed so the crew would get their required rest. This is of course is just an example reserves have different rest periods then lineholders. Now for how many hours a FA works all depends on their schedule. Some will work the 83 hours, some less, some more.