Why the schedule starts before takeoff
An airline’s published flight duration is usually a block time: the planned interval between leaving the departure gate and reaching the arrival gate. “Block” refers to the blocks once used to secure an aircraft while parked. The measure describes the whole trip the airline must operate, not just the portion spent cruising through the air.
That distinction matters because taxiing is not a fixed-length prelude. A plane may wait for other aircraft, follow a long route to a runway, or pause for traffic control. After landing, it may need to cross active runways or wait for an open gate. Those minutes depend on the airport and the conditions that day.
A schedule has to work on the ground, too
Airlines use expected taxi time when planning a flight, alongside expected time in the air. The estimate gives the operation room to account for ordinary ground movement rather than promising a duration based only on ideal flying conditions. Actual taxi time can still be shorter or longer, so a flight may arrive ahead of or behind its posted time without its airborne portion changing much.
Block time also connects one flight to the next. The aircraft and crew have to reach the gate before they can prepare for another departure; a schedule built around air time alone would leave those ground movements out of the plan. The result is a clock that measures the trip passengers experience from gate departure to gate arrival—including the slow, unglamorous minutes that make the next takeoff possible.
