When a passenger travels on a flight without a prior reservation for that specific flight.
On most modern airlines, flying standby occurs when a passenger travels on a flight without a prior reservation for that specific flight. There are two circumstances in which passengers typically fly standby. First, a missed flight may require a passenger to fly standby on the next flight to the same destination, as he or she now lacks a reservation. Secondly, a passenger may arrive at the airport early (whether accidentally or on purpose) and wish to take an earlier flight listed for that day. He or she will then attempt to travel standby on the earlier flight, and failing that, proceed to take his or her booked flight.
