Hi, Myself Gloria Brooks, I am an energetic voyager. While excitedly booking a flight we never tend to think about cancelling it, but under certain circumstances we have to. United airlines cancellation policy covers all that you should be aware of, if you have any desire to drop your United flight ticket. You can demand the flight cancellation as long as 3 hours before the booked takeoff for global flights and 2 hours for trips inside the United States.