Originally Posted by UAL_Rulez
Times shown in airline timetables and on their flight status systems (web site, automated phone info line, airport monitors etc.) are gate departure/arrival times.
I remember some years back it came out in the MSP press that NW had a policy that planes would be pushed back from the gate on time, even if ATC had their takeoff delayed and they knew they'd have to sit on the runway. This let them claim an 'on-time departure', even if the plane took off much later than scheduled.