In addition there are so many variables that go into a flight. A common problem in the tropical airports is weight restricted flights. Once the temperature gets too high air density gets lower and the wings generate less lift. The captain has to decide between the passengers, cargo, and luggage. Flying out of MIA and BKK, whenever I heard the announcement the flight was weight restricted I knew some poor sap is definitely not picking up his bags at the other end. Flying non-rev and being the last to get checked in and boarded meant that sap was probably me.