Referring to something taking place before a plane takes off: After all the passengers were on board the aircraft, and before lifting off, the travellers could read the preflight safety information in a pamphlet in the pouch of the seat back.

The examination or inspection of a plane before takeoff: Preflights were required for each plane before the passengers were allowed on board for departure.

To inspect or to perform a check-up of a plane before departure: It is mandatory that aircrafts are preflighted and examined before takeoff.