United Airlines provides a 24-hour cancellation policy, you can cancel your flight in between 24 hours of ticket confirmation dial. If you want to cancel your flight you are able to do so free of charge within 24 hours of the date of your reservation. United airlines provides a 24-hour cancellation policy, you can cancel your flight through dialling. If you want to cancel your flight dial you are able to do so free of charge within 24 hours of the date of your reservation.