Flight time is defined by International Civil Aviation Organization (ICAO) as The total time from the moment an aeroplane first moves for the purpose of taking off until the moment it finally comes to rest at the end of the flight, and thus includes time spent taxiing and performing pre-flight checks on the ground, ...

According to the FAA (14 CFR § 1.1) and most global aviation authorities, "flight time" is defined as the period that commences when an aircraft moves under its own power for the purpose of flight and ends when the aircraft comes to rest after landing. This is commonly referred to in the industry as "Block-to-Block" or "Chock-to-Chock" time. It includes the time spent taxiing from the gate to the runway and the time spent taxiing back to the gate after touchdown. It does not include the time passengers spend boarding while the plane is stationary, nor does it include "ground delays" where the engines are off. For pilots, this definition is critical because it is the time they "log" in their logbooks to meet experience requirements and is also used to calculate legal "duty time" limits to prevent fatigue. For passengers, "flight time" usually refers to the total duration from gate departure to gate arrival, which is why your flight might be scheduled for 3 hours even if you are only in the air for 2 hours and 15 minutes.