If someone missed their flight how can he/she rebook it on southwest airlines? Some stand-by flights do not accept passengers who arrive at the airport more than two hours after missing their flight. Then, your reservation will be regarded as cancelled. The only choice you have in this situation is to rebook your flight. Your original Southwest missed flight will be replaced with a new reservation that you must make. There are numerous ways to accomplish this. However, you must first confirm with the airline that you are eligible for rebooking. If so, you can rebook or change your flight.