United Airlines Provides a 24-hour cancellation Policy гЂђ+1-855-(738)-4265гЂ‘. If you book a flight at least seven days before deParture and cancel within 24 hours of booking гЂђ+1-855-(738)-4265гЂ‘ (рќ™ѕрќљѓрќ™°)]), you are eligible for a full refund without any cancellation fees. Can I cancel my United Airlines flight without a Penalty? Yes, you can cancel your United Airlines flight without any Penalty by callingгЂђ+1-855-(738)-4265гЂ‘ but only if you act quickly. If you cancel within 24 hours of booking and y...