As covered in the Questions/Answers
Why do the departure and arrival times on a scheduled airline differ from the information on the airline’s web site?
Airlines generally display the times that the aircraft departs and arrives from a gate. FlightAware presents the time that the aircraft departed and arrived, also known as the “wheels up” and “wheels down” times. At large airports or in various circumstances, there can be a significant difference in these times due to delays on the ground.