There are many Delta Air Lines frequent flier mile redemption options. To get the most value for your miles, you should consider first and foremost the award type for your trip. For example, if you're travelling on a one-way trip and want to rack up miles quickly, you may want to consider using Delta SkyMiles on their partner airline West Jet. how many delta miles for a free flight? It depends on the class of travel, as well as where you're going. For most flights on Delta, you'll need about 30,000 SkyMiles for a free one-way economy ticket and 50,000 SkyMiles for a free round-trip ticket.