We sat on the taxiway for 3 hours several years ago and finally took off to the west-this was a JetBlue flight. I asked a friend that is a commercial airline pilot what would have caused the delay? He said that weight-wind and temperature affect a planes lift and that when over weight you either remove people, bags or go out to the west. Going out to the west requires lower wind speeds from the east or you don't get the lift. He noted that during regatta you will see most airlines using the larger Airbus or Boeing aircraft to avoid weight-wind or temperature delays. Lastly he said that when going out to the west pilots have to get a special clearance from air traffic control in the states as they will be entering air traffic routes from a different path. Confusing to me.