staying in the air; remaining airborne
Used for aircraft, birds, or objects that maintain flight or hang in the air; often appears in compound terms like 滞空時間 (time aloft).
This airplane's time aloft is about 12 hours.
The bird is staying in the air riding the wind.
flight duration; time in the air
flight record; endurance record (in the air)
Compound of 滞 (stay, stagnate) and 空 (sky, air). The kanji combination directly conveys the meaning of remaining in the air.