Delta Air Lines Inc., American airline incorporated on Dec. 31, 1930, as Delta Air Corporation, which adopted the current name in 1945. Engaged initially in agricultural dusting operations in the southern United States and in Mexico, it progressed, especially after 1934, to transporting passengers and cargo throughout the southeastern United States. By 1970, Delta had an all-jet fleet, and in 1972 it acquired Northeast Airlines. Trans-Atlantic service began in 1978 with the first nonstop flights from Atlanta to London. In 1981, Delta launched a frequent-flyer program. In 1987, it acquired Western Airlines, and that same year Delta began trans-Pacific service (Atlanta-Portland, Oregon-Tokyo). In 1990, Delta was the first airline in the United States to fly McDonnell Douglas MD-11 jets. In 1991, it acquired substantially all of Pan Am's trans-Atlantic routes and the Pan Am Shuttle, rebranded as the Delta Shuttle.

Delta One:

Delta One is the airline's premier business class product, available on long-haul international flights, as well as transcontinental service from New York–Kennedy to Los Angeles, San Francisco and Seattle/Tacoma. Delta One features lie-flat seating on all aircraft types, and direct aisle access from every seat on all types except the Boeing 757-200. All seats are also equipped with a personal, on demand in-flight-entertainment (IFE) system, universal power-ports, a movable reading light, and a folding work table. Passengers also receive complimentary chef-curated meals, refreshments, alcoholic beverages, an amenity kit, premium bedding, and pre-flight Sky Club access.

Premium Select:

Premium Select, this cabin will feature extra legroom; adjustable leg rests; extra seat pitch, width, and recline; and a new premium service. Delta introduced it on its new Airbus A350, first delivered in fall 2017, to be followed by the now-retired Boeing 777.

First Class:

First Class is offered on mainline domestic flights (except those featuring Delta One service), select short- and medium-haul international flights, and Delta Connection aircraft. Seats range from 18.5 to 20.75 inches (47.0 to 52.7 cm) wide and have between 37 and 40 inches (94 and 102 cm) of pitch. Passengers in this class receive a wider variety of free snacks compared to Main Cabin, as well as free drinks and alcohol, and full meal service on flights 900 miles (1,400 km) and longer.

Delta Comfort+:

Delta Comfort+ seats are installed on all aircraft and feature 34–36 inches (860–910 mm) of pitch; on all Delta One configured aircraft, 35–36 inches (890–910 mm) of pitch and 50 percent more recline over standard Main Cabin seats. Additional amenities include: priority boarding, dedicated overhead space, complimentary beer, wine, and spirits on flights 250 miles (400 km) or more, and complimentary premium snacks on flights 900 miles (1,400 km) or more. Complimentary premium entertainment is available via Delta Studio, with free headsets available on most flights.

Main Cabin:

Main Cabin (Economy Class) is available on all aircraft with seats ranging from 17 to 18.6 inches (43 to 47 cm) wide and 30 to 33 inches (76 to 84 cm) of pitch. Main Cabin passengers receive complimentary snacks and non-alcoholic drinks on all flights 250 miles (400 km) or longer. Alcoholic beverages are also available for purchase. Complimentary meals and alcoholic drinks are provided on long-haul international flights as well as selected transcontinental domestic flights, such as between New York–JFK and Seattle, San Francisco, Los Angeles, and San Diego.

Basic Economy:

Basic Economy is a basic version of Main Cabin, offering the same services with fewer flexibility options for a lower price. Examples of fewer flexibility options include no ticket changes, no paid or complimentary upgrades regardless of frequent-flier status, and only having a seat assigned at check-in. As of December 2021, Basic Economy travelers no longer earn award miles.

Delta has nine hubs, with Atlanta being its largest in terms of total passengers and number of departures. It is ranked second among the world's largest airlines by number of scheduled passengers carried, revenue passenger-kilometers flown, and fleet size. Delta operates the largest Boeing 717, Boeing 757, and Boeing 767 fleets in the world, and the largest Airbus A330 fleet of any US airline. Delta operates the largest Boeing 717, Boeing 757, and Boeing 767 fleets in the world, and the largest Airbus A330 fleet of any US airline. Prior to its 2008 merger with Northwest Airlines, Delta's fleet was made up of solely Boeing and McDonnell Douglas aircraft. Airbus aircraft from Northwest joined the fleet after the merger, and more have since been added.