How is "Flight Time" defined?

"Flight Time" is defined as the total time from takeoff to touchdown. This specific definition encompasses the entire phase of flight during which the aircraft is airborne, starting when the aircraft lifts off the ground and concluding when it touches down at its destination. This period includes all aspects of the flight such as climbing, cruising, and descending, which are all critical for assessing overall flight operations and performance.

The other choices do not accurately capture the definition of flight time. For instance, measuring from engine start to takeoff would not account for the actual airborne segment of the flight. Similarly, the time spent in the air after takeoff alone does not signify the total period of flight as it excludes the landing phase. Lastly, the duration while the aircraft is parked is irrelevant to flight time, as it does not involve any airborne activity. Thus, the definition provided in the correct answer is comprehensive and directly aligns with standard aviation terminology.