Hello, I am Michael robert live in the USA and I am a Frequent Traveler. I work for AirTravelPolicy.
As per United Airlines Cancellation Policy, You can cancel travel up to 24 hours before the scheduled flight departure. If you cancel your reservation, United will refund your purchase, but it may keep 10% of the fare. The Right of Withdrawal does not apply to promotional fares, so please refer to the fare rules for your ticket.
Check other Airlines policies