If you book your Delta flight directly through delta.com[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] the Fly Delta app[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] or Delta customer service[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you have 24 hours from the time of booking to cancel your reservation without incurring any fees. This applies to all fare types[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] including non-refundable and Basic Economy tickets. If your flight departs at least 7 days after booking[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you are also eligible for a full refund.
Condé Nast Traveler
Refundable/Flex Tickets
If you purchased a refundable or Flex ticket[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you can cancel your flight at any time before departure without penalty. You will receive a full refund to your original form of payment.
ApSense

International Flights (Excluding Basic Economy)
Delta has eliminated change fees for international flights originating in North or South America to anywhere in the world[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] in all cabins except Basic Economy.
content.delta.com

Basic Economy Tickets
Basic Economy tickets are the most restrictive fare class. They do not allow changes or cancellations after the 24-hour risk-free period. If you cancel a Basic Economy ticket within 24 hours of booking[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you will receive a full refund. After that period[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] the ticket is non-refundable.
Delta News Hub
Non-Refundable Tickets
For non-refundable tickets[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] if you cancel within the 24-hour risk-free period[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you will receive a full refund. After that period[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] you can cancel your flight and receive an eCredit for the remaining value[+𝟭-𝟴𝟬𝟭 𝟴𝟱𝟱 𝟱𝟵𝟬𝟱] minus any applicable cancellation fees. The cancellation fee varies depending on the origin of your flight:
Delta Air Lines