Flight Time is the amount of time you spend off the ground between strides when running.
Flight Time is the opposite of Ground Contact Time, as it's a measurement of the amount of time you are not in contact with the ground with each step. It can be used to analyze your running form. It's generally considered beneficial to spend more time in the air and less time on the ground when running.
Find it in SportTracks
If you track runs with a sensor that records Ground Contact Time, Flight Time can be found on your Workout Detail pages: