In many cases, yes. You may qualify for Risk-free Cancellation. If so, you can cancel your itinerary. Otherwise, you can request a refund for eTickets here at delta.com if the tickets were:
- Refundable
- Purchased with a credit card
- Purchased with cash or check. (U... or Canadian currency only)
- Not obtained with a SkyMiles award
- Issued with a ticket number that begins with 006 followed by 10 digits