Airlines will only consider documents on an official hospital letterhead, signed and typed by a doctor. The document must provide a diagnosis and include the doctor's name and signature. Prescriptions are not accepted as valid documentation.

To cancel a flight due to illness in 2026, you must first contact the airline's customer service department or use their mobile app to initiate a "Cancellation for Medical Reasons." Most airlines will require a formal medical certificate or a signed letter from a licensed physician on official hospital letterhead, detailing the diagnosis and stating that you are "unfit to travel." Standard prescriptions or pharmacy notes are generally not accepted as valid proof. If you have a non-refundable ticket, the airline may not offer a cash refund but will often provide a Travel Credit or "voucher" valid for 12 months, waiving the usual cancellation fees. For the best protection, travelers are encouraged to use travel insurance or "Cancel for Any Reason" (CFAR) coverage, which simplifies the reimbursement process without requiring extensive medical documentation to be shared with the airline.