SkyMiles is the mileage and status program from Delta Air Lines. It is obviously essential for Delta frequent fliers but also popular with other SkyTeam alliance frequent travelers. The US loyalty programs are among the most established, so are attractive as well to other airline users.
The main US airline loyalty programs are all now very similar, having mostly switched to a revenue-based earning system for their own flights. With SkyMiles, you need to be especially careful with…