Within 24 hours of the time of booking, Singapore Airlines allows customers to cancel their tickets without penalty. If you're unsure of how to cancel Singapore Airlines flight, one of the easiest ways is to call the airline's customer service line, request a cancellation, and then request a refund. It can take up to two hours to cancel a flight over the phone; if you experience any problems, you can also use the airline's official website to make the change. Keep in mind that if your flight is close to departure, you frequently won't be able to change it.