noun
flying overnight; spending a night on a plane
Refers to the act of staying overnight on an airplane, typically during a long-haul flight. Often used in travel contexts.
機中泊を含むツアーを予約した。
I booked a tour that includes an overnight flight.
機中泊は疲れるが、朝には現地に着く。
Spending a night on a plane is tiring, but you arrive at the destination in the morning.
船中泊 means spending a night on a ship, whereas 機中泊 is for airplanes.
Compound of 機中 (in the airplane) + 泊 (overnight stay). The exact historical derivation is uncertain, but it follows the pattern of similar compounds like 車中泊 and 船中泊.