Can't speak for everybody but we get paid from the time we leave the gate until we block in at the arrival city. If we're late we get the extra time, if we're early we get what the flight was actually scheduled for. Our per diem starts at our check in time for the trip, 1 hour before departure on domestic and 1 1/2 hrs before international and ends 15 minutes after block in of our last flight. No pay for boarding, or sitting at the gate delayed for maintenance, weather or ATC. Our typical 4 day trip pays 20 hrs.