When referring to a roller coaster, the sensation of coming out of your seat. This is caused by negative vertical g's, which counteract the force of gravity. This usually happens when cresting a hill near the front of the train, or descending when near the rear. An important part of the fun factor.

In aviation, air time is the time from when the wheels leave the ground to the time they touch down again.

This is not to be confused with flight time, which begins when an aircraft begins moving for the purpose of flight.