Delta Air Lines is an American airline headquartered in Atlanta and the world's largest airline by fleet size, destination, and passenger revenue. Delta operates an extensive domestic and international network, spanning North America, South America, Europe, Asia, Africa, the Middle East, the Caribbean, and Australia. Delta and the Delta Connection carriers fly to 367 destinations in 65 countries (excluding codeshare), across six continents. Delta operates its largest hubs at Hartsfield-Jackson Atlanta International Airport and Detroit Metropolitan Wayne County Airport. Delta Air Lines is a founder and part of the SkyTeam airline alliance.

Prior to merging with Northwest Airlines, Delta Air Lines had an all-Boeing (including McDonnell Douglas aircraft) fleet. Delta inherited numerous Airbus aircraft in its merger with Northwest Airlines. Delta was one of the last major airlines to operate the original Boeing 737–200 models, until the last of these aircraft were retired in 2006. Delta has the largest fleets of Boeing 757 and Boeing 767 and is the largest US operator of the Airbus A330 aircraft of any airline. It is the second largest operator of the McDonnell Douglas MD-80 (behind American Airlines), the largest operator of the Boeing 767–300, and the larger of the two operators of the 767-400ER.

SkyMiles is Delta's frequent flyer program. Created in 1981 as the "Delta Air Lines Frequent Flyer Program"; its name was changed to SkyMiles in 1995. When the frequent flyer program was first established in 1981, new members were awarded an enrollment bonus of 10,000 miles. In 2006, SkyMiles was picked as the "best frequent flyer program" in the Best in Business Travel Awards.