You must understand the terms of Delta&039;s cancellation policy if you have purchased a ticket with them and want to cancel it. You may find answers to your questions about Delta Airlines&039; cancellation policy and the requirements needed to be eligible for full refunds on this page. You may cancel your flight reservation with Delta Airlines if you have a medical emergency or other pressing matter. This policy is applicable to customers who become unwell unexpectedly prior to their flight and are unable to travel as a result. However, you must cancel your flight before it takes off, and you must be able to provide proper paperwork (such as a medical certificate) to support your claim.