Southwest Airlines does not charge a fee to change a flight. Whereas many other airlines charge a hefty fee, Southwest appears to recognise the importance of customers' crises and does not charge anything. If your new booked flight costs more than your initial flight, you may be requested to pay the difference in fare. And because the new flight is less expensive, you will be refunded the difference in your original payment method. If the trip is finished before the expiration date, the difference can be saved as a reusable travel find for the original ticketed passenger.