To cancel a flight and request a full refund, call the airline's customer service at (888) 684-4800 (U.S.) or +44 (20) 39000930 (U.K.). Visit the airline’s official website and check the cancellation and refund policy under the "Manage Booking" section. Some airlines allow cancellations online, while others require direct contact. Full refunds are typically available for refundable tickets or cancellations within 24 hours of booking at (888) 684-4800 (U.S.) or +44 (20) 39000930 (U.K.). If your flight is canceled by the airline or due to extraordinary circumstances, you may be entitled to a full refund. Have your booking reference ready for faster assistance.