Yes, you can use Delta SkyMiles to upgrade to First Class, and in 2026, Delta has made this process more "self-service" than ever before. There are two primary ways: "Upgrade with Miles" during the booking process or "Mileage Upgrade Awards" after booking. If your reservation is eligible, you will see a "Select Seats" option in the Fly Delta app where you can view First Class or Delta One seats and choose to pay for them with a fixed amount of miles instead of cash. The "cost" in miles is dynamic and usually follows the cash price of the seat (roughly 1.2 to 1.5 cents per mile in value). However, be aware that "Basic Economy" (E class) tickets are generally not eligible for mileage upgrades. If you are a Medallion member, you may also be eligible for "Complimentary Upgrades," but using miles allows you to "confirm" your seat immediately rather than waiting for the upgrade window to open 24–120 hours before your flight.