This has probably been discussed in the past, but I’m new so I’ll ask again. What determines when a commercial flight has an on-time departure and an on-time arrival? Does departure start when the boarding door is closed or when push-back starts? Does arrival start when the plane touches down or when the boarding door is opened for deplaning?
I’m using FlightAware to look back at some flights I was on and the departures and arrivals and duration sure don’t match up with what I encountered. Do the pilots “fudge” on reporting the times? 
Departure time is counted from the gate. To be on time, the aircraft must depart within 15 minutes of the scheduled time. Same thing for arrivals - the arrival time is at the gate and is considered on time if it is within 15 minutes.
If you read the Questions/Answers for FlightAware you will find out why there is a difference between the times the airline reports and that FlightAware reports.
More specifically, FlightAware only concerns itself with actual flight time. We’re reporting “wheels up” to “wheels down” and make no attempt to incorporate any other aspect of a commercial flight.
Taxi times and ground sequencing delays can be a large portion of a flight, especially at a busy airport, which is factored in to the airline’s reported arrival and departure times. To the airline, departure is when the cabin door closes and the plane pushes back from the gate. To FlightAware the departure time is when the wheels actually leave the ground.
DAMIROSS/NUGGET…Thanks for your replies. I’ll now go to the individual airlines and query them on posted departure and arrival times. My 35-minute wheels-up to touch down flights from CAE to ATL are posted mostly as 55 to 60-minutes door to door by DL pilots, but actual is more like 1 hour, 20 minutes - door to door. Some ground time/taxiing is so painfullly long! The new south runway at ATL adds 5 - 15 minutes additional taxiing time.