Delta Air Lines customers with flight credits on the books from the airline now will have until Dec. 31, 2023, to rebook their ticket for travel through 2024, according to the carrier. The extension is effective immediately. Customers with e-credit documents should see the new expiration date soon if it hasn't already been updated, according to Delta. In addition, the extension applies to customers with upcoming 2022 tickets and those who purchase a ticket this year, in case their travel plans change. Tickets usually have a one-year validity.