The number of Delta SkyMiles needed for a free flight varies widely due to Delta's dynamic pricing model, which bases mileage costs on demand, origin, destination, and travel dates.

• For domestic one-way economy flights, you can find awards starting as low as about 5,000 miles, but some can cost over 100,000 miles

• International economy flights typically start around 20,000 miles but can go much higher depending on the route and class

• Business or first-class awards generally start at around 15,000 miles and can exceed 400,000 miles one-way

• Delta does not publish a fixed award chart, so mileage requirements fluctuate with ticket prices

• Delta offers a TakeOff 15 program giving eligible credit card holders 15% off award flights, effectively reducing the miles needed

• There is no minimum number of miles required to redeem for a flight, but for Delta Amex cardholders using the Pay With Miles feature, a minimum of 5,000 miles per passenger is required

In summary, for a free Delta flight, expect to need at least 5,000 SkyMiles for short domestic trips, with mileage increasing significantly for longer or premium cabin flights depending on dynamic pricing factors.