On most modern airlines, flying standby is when a passenger without a seat assignment waits at the gate to see if there is an extra seat after all scheduled passengers have boarded.

In 2026, being on "standby" does not always mean the flight is physically full, but it does mean that all confirmed seats have been allocated. There are two main types of standby. Revenue Standby occurs when a passenger wants to switch to an earlier or later flight on the same day; they are put on a list to see if a seat becomes available due to a "no-show" or a cancellation. Staff/Non-Revenue Standby is for airline employees who only get a seat if there is one left over after all paying passengers have boarded. However, if you are a paying passenger and your boarding pass says "Standby" or "Seat Assigned at Gate," it often means the flight is overbooked. Airlines frequently sell more tickets than there are seats, betting that a certain percentage of people won't show up. In this scenario, you are "standing by" for a seat that has already been sold to someone else who might not arrive. If everyone shows up, the flight is indeed full, and the airline will begin asking for volunteers to take a later flight in exchange for compensation. So, while standby is a strong indicator of a full flight, it is technically a waiting list for the availability of a seat.