Delta Air Lines, Inc. ("Delta"; NYSE: DAL) is a major American airline, with its headquarters and largest hub at Hartsfield–Jackson Atlanta International Airport in Atlanta, Georgia. The airline along with its subsidiaries and regional affiliates operate over 5,400 flights daily and serve an extensive domestic and international network that includes 319 destinations in 54 countries on six continents, as of October 2016. Delta is one of the four founding members of the SkyTeam airline alliance, and operates joint ventures with AeroMexico, Air France-KLM, Alitalia, Korean Air, Virgin Atlantic, and Virgin Australia. Regional service is operated under the brand name Delta Connection.

One of the three remaining legacy carriers, Delta is the sixth-oldest operating airline by foundation date, and the oldest airline still operating in the United States. The company's history can be traced back to Huff Daland Dusters, founded in 1924 in Macon, Georgia as a crop dusting operation. The company moved to Monroe, Louisiana, and was later renamed Delta Air Services, in reference to the nearby Mississippi Delta region, and commenced passenger services on June 17, 1929. Among predecessors of today's Delta Air Lines, Western Airlines and Northwest Airlines began flying passengers in 1926 and 1927, respectively.

In 2013, Delta Air Lines was the world's largest airline in terms of scheduled passengers carried (120.6 million), and the second-largest in terms of both revenue passenger-kilometers flown (277.6 billion) and capacity (4.4 billion ASM/week; March 2013).

Delta Air Lines began as a crop dusting operation called Huff Daland Dusters, Incorporated. The company was founded on May 30, 1924 in Macon, Georgia, and moved to Monroe, Louisiana, in 1925. They flew a Huff-Daland Duster, the first true crop duster, designed to combat the boll weevil infestation of cotton crops. Collett E. Woolman, one of the original directors, purchased the company on September 13, 1928, and renamed it Delta Air Service. Service began on June 17, 1929 with the inaugural flight between Dallas, Texas and Jackson, Mississippi.

Delta moved its headquarters to its current location in Atlanta in 1941, and continued to grow through the addition of routes and the acquisition of other airlines. They replaced propeller planes with jets in the 1960s and entered international competition to Europe in the 1970s and across the Pacific in the 1980s.

Delta's more recent history is marked by its emergence from bankruptcy on April 25, 2007, and the subsequent merger with Northwest Airlines. The merger was announced April 14, 2008, and was set to create the world's largest airline. After approval of the merger on October 29, 2008, Northwest continued to operate as a wholly owned subsidiary of Delta until December 31, 2009 when both carriers' operating certificates were merged (the Delta certificate was kept). Delta completed the integration with Northwest on January 31, 2010 when their reservation systems and websites were combined, and the Northwest Airlines name and brand were officially retired.

Delta Air Lines as it exists today is the result of numerous mergers over its history. Predecessor carriers forming the current Delta Air Lines include:

Delta's corporate headquarters is located on a corporate campus on the northern boundary of Hartsfield-Jackson Atlanta International Airport, within the city limits of Atlanta. This location has served as Delta's headquarters since 1941, when the company relocated its corporate offices from Monroe, Louisiana, to Greater Atlanta. The crop dusting division of Delta remained headquartered in Monroe until Delta ceased crop dusting in 1966. Prior to 1981, the Delta corporate campus, an 80-acre (32 ha) plot of land in proximity to the old Hartsfield Airport terminal, was outside the City of Atlanta limits in unincorporated Fulton County. On August 3, 1981 the Atlanta City Council approved the annexation of 141 acres (57 ha) of land, an area containing the Delta headquarters. As of 1981 Delta would have had to begin paying $200,000 annually to the City of Atlanta in taxes. In September 1981 the airline sued the city, challenging the annexation on the basis of the constitutionality of the 1960 City of Atlanta annexation of the Hartsfield old terminal. The City of Atlanta was only permitted to annex areas that are adjacent to areas already in the Atlanta city limits.

In addition to hosting Delta's corporate headquarters, Hartsfield-Jackson is also the home of Delta TechOps, the airline's primary maintenance, repair and overhaul arm and the largest full-service airline MRO in North America, specializing in engines, components, airframe and line maintenance.

Delta maintains a large presence in the Twin Cities, with over 12,000 employees in the region as well as significant corporate support functions housed in the Minneapolis area, including the company's information technology divisional offices.

Delta's logo, often called the "widget", was originally unveiled in 1959. Its triangle shape is taken from the Greek letter delta, and recalls the airline's origins in the Mississippi Delta. It is also said to be reminiscent of the swept-wing design of the DC-8, Delta's first jet aircraft.

Delta's current livery is called "Upward & Onward". It features a white fuselage with the company's name in blue lettering, and a widget on the vertical stabilizer. Delta introduced its current livery in 2007 as part of a re-branding after it emerged from bankruptcy. The new livery consists of four colors, while the old one (called "colors in motion") used eight. This meant the switch saved the airline money by removing one day from each aircraft's painting cycle. The airline took four years to repaint all of its aircraft into the current scheme, including aircraft inherited from Northwest Airlines.

Delta has ten domestic hubs and four international hubs. Delta carries more passengers than any other airline at Atlanta, Cincinnati, Detroit, Minneapolis/St. Paul, New York-JFK, New York-LaGuardia, and Salt Lake City.

These statistics are current as of February 2017. (Ranked by daily departures).

Between its mainline operation and subsidiaries, and as of March 2015, Delta employs nearly 80,000 people. Joanne Smith is Executive Vice President and Chief Human Resources Officer responsible for the oversight and support of personnel needs at Delta. She was appointed on October 1, 2014 replacing Mike Campbell.

Delta's 12,000 mainline pilots are represented by the Air Line Pilots Association, International and are the union's largest pilot group. The company's approximately 180 flight dispatchers are represented by the Professional Airline Flight Control Association (PAFCA).

Not counting the pilots and flight dispatchers, Delta is the only one of the five largest airlines in the United States, and one of only two in the top 9 (the other being JetBlue), whose non-pilot USA domestic staff is entirely non-union.

The non-pilot non-unionization caused issues during and after the merger with Northwest, whose employees had a much higher rate of unionization. While pilots at both airlines were unionized, it was necessary to hold unionization votes for all other groups of employees. Northwest Airlines flight attendants were formerly represented by the Association of Flight Attendants (AFA). A vote on unionization with the AFA at the post-merger Delta was held on 3 November 2010, unionization was narrowly rejected by flight attendants, with 9,544 votes against unionization and 9,216 in favor. The AFA accused Delta of interference in the vote and requested the National Mediation Board (NMB) investigate and order a second vote. The NMB investigation found that the election was not compromised and dismissed the claim. Currently both the International Association of Machinists and Aerospace Workers and a coalition of the AFA and the Transport Workers Union of America are seeking to hold unionization votes for Delta flight attendants.

As of March 2015, Delta operates more than 5,400 flights per day. Delta Connection operates 2,533 daily flights.

Delta is the only U.S. carrier that is flying to Accra, Copenhagen, Dakar, Dusseldorf, Johannesburg, Lagos, Nice, Prague, Reykjavik, and Stuttgart. It is also the only US carrier that has scheduled service to Africa.

Delta was a founding member of the SkyTeam Alliance in 2000. In addition to SkyTeam partners, Delta Air Lines also has codeshare agreements with the following airlines:

Inherited from the Northwest-KLM relationship (which is older than any of the three major airline alliances including SkyTeam itself), Delta has a transatlantic joint venture with Air France-KLM and Alitalia. The program coordinates transatlantic operations, including ticket pricing, schedules, capacity, and revenue. On January 27, 2012, the European Commission launched an investigation into the impact of the joint venture on competition on the routes that it covers.

On December 11, 2012, Delta announced that it would spend $360 million to acquire a 49 percent stake in Virgin Atlantic. These shares were previously held by Singapore Airlines. As a part of this agreement, both airlines would share the costs and revenues from all of the joint venture flights the airlines operated. The two airlines planned to operate a total of 31 roundtrip flights between the UK and North America, including nine daily roundtrip flights between London Heathrow and New York City airports (John F. Kennedy International Airport and Newark Liberty International Airport). The two airlines' application for antitrust immunity was granted by the United States Department of Transportation on September 23, 2013.

As of January 2013, Delta operates a fleet of more than 800 aircraft manufactured by Airbus, Boeing, and McDonnell Douglas. Delta operates the largest Boeing 717, Boeing 757, Boeing 767, McDonnell Douglas MD-88, and McDonnell Douglas MD-90 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.

Unlike other U.S. legacy carriers, Delta often seeks to acquire and utilize older aircraft, especially narrow-bodies, and they have created an extensive MRO (maintenance, repair and overhaul) organization, called TechOps, to support them. The oldest aircraft in the fleet are the McDonnell Douglas MD-88s, with an average age of over 25 years. However, in early 2011, Delta began talks with Airbus, Boeing and Bombardier to discuss replacing the McDonnell Douglas DC-9s, MD-88s, and older A320 and 757-200 aircraft. On August 22, 2011, Delta placed an order for 100 Boeing 737-900ER aircraft and deferred an order of 100 small narrow-body jets until 2012.

As part of its strategy to utilize less expensive used airplanes, Delta agreed in 2012 to lease 88 Boeing 717s acquired by Southwest Airlines during their acquisition of AirTran Airways. They would be used as replacements for the DC-9 fleet and some 50-seat regional aircraft like the CRJ-100 and -200. The first revenue flight was on October 25, 2013, Delta officially retired its last DC-9 on January 6, 2014; it was used on an as-needed basis until January 22, 2014 when the last one was removed from service. Delta was the final US carrier operating the DC-9. As a continuation of the narrowbody fleet refresh and expansion, Delta ordered 75 Bombardier CS100 aircraft and an additional 50 options on April 28, 2016, becoming the first American carrier to order the type.

The airline has not been as keen to acquire or operate aging widebody aircraft. On August 1, 2014, Delta announced they would begin to retire the aging Boeing 747-400 fleet, acquired as part of the Northwest merger. During a 2014 earnings call, CEO Richard Anderson announced that they would be retired by the end of 2017. On November 20, 2014, the airline announced an order for 25 Airbus A350-900 and 25 Airbus A330-900 aircraft to replace the 747 fleet as it was retired, as well as some aging 767s. A350 deliveries began in the second quarter of 2017, while the first A330-900 is scheduled for 2019.

Delta underwent a cabin branding upgrade in 2015. The airline now offers or plans to offer 6 different cabin service options: Delta One, Delta Premium Select, First Class, Comfort+, Main Cabin, and Basic Economy. Availability and exact details vary by route and aircraft type.

Delta One is the airline's premier business class product, being available on long haul international flights, as well as transcontinental service from New York-JFK to Los Angeles and San Francisco.

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. The Boeing 767-300ER and Boeing 767-400ER seats, designed by James Thompson, feature a space-saving design whereby the seats are staggered such that when in the fully flat position, the foot of each bed extends under the armrests of the seat in front of it. Delta one cabins on the Boeing 777-200ER/LR fleet are configured in a Herringbone layout, while all Boeing 747-400 and Airbus A330 cabins (featuring the Cirrus flat-bed sleeper suite by Zodiac Seats U.S.) are configured in a reverse herringbone pattern.

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.

In August 2016, Delta announced the introduction of Delta One Suites on select widebody fleets. The suites will feature a door to the aisle for enhanced privacy, as well as improved storage space, a larger IFE screen, and updated design. The suites will roll out on the Airbus A350 fleet, slated to begin delivery in fall 2017, followed by the Boeing 777.

In April 2016, CEO Ed Bastian announced that a new Premium Economy cabin will be added. Since renamed to Premium Select, this cabin will feature extra legroom, adjustable leg rests, extra seat pitch, width, and recline, and a new premium service. Delta will introduce it on its new Airbus A350, slated for delivery in Fall 2017, followed by the Boeing 777.

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 with more than 50 seats. 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 and longer. Certain aircraft also feature power-ports at each seat and free entertainment products from Delta Studio. First Class passengers are also eligible for priority boarding.

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: Sky Priority Boarding, dedicated overhead space, complimentary beer, wine, and spirits on flight 250 miles or more, and complimentary premium snacks on flights 900 miles or more. Complimentary premium entertainment is available via Delta Studio, with free headsets available on most flights. On transcontinental flights between JFK-LAX/SFO, Delta Comfort+ passengers also get Luvo snack wraps. Medallion members can upgrade from Main Cabin to Comfort+ for free, while other customers can upgrade for a fee or with SkyMiles.

Main Cabin (also known as "Economy Class") is available on all aircraft with seats ranging from 17 to 18 inches (43 to 46 cm) wide and 30 to 33 inches (76 to 84 cm) of pitch. The main cabin on Boeing 737, 747-400, 777, and selected Boeing 757-200, 767-300, and McDonnell Douglas MD-90 aircraft have an articulating seat bottom where the seat bottom moves forward in addition to the seat back tilting backwards when reclining.

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. As part of Delta's Flight Fuel buy on board program, meals are available for purchase on other North American flights 900 miles (1,400 km) or longer.

Delta operated a different buy on board program between 2003 and 2005. The previous program had items from differing providers, depending on the origin and destination of the flight. Prices ranged up to $10 ($12.68 when adjusted for inflation). The airline started the service on a few selected flights in July 2003, and the meal service was initially offered on 400 flights. Delta ended this buy on board program in 2005; instead, Delta began offering snacks at no extra charge on flights over 90 minutes to most U.S. domestic flights and some flights to the Caribbean and Latin America. Beginning in mid-March 2005 the airline planned to stop providing pillows on flights within the 49 contiguous U.S. states, Bermuda, Canada, the Caribbean, and Central America. In addition, the airline increased the price of alcoholic beverages on Delta mainline flights from $4 ($4.91 when adjusted for inflation) to $5 ($6.13 when adjusted for inflation); the increase in alcohol prices did not occur on Song flights.

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.

On August 5, 2008, Delta announced it would be installing the Aircell mobile broadband network, Gogo, which enables customers traveling with Wi-Fi enabled devices, such as laptops, smartphones, and tablets, to access the Internet for a fee. Gogo was initially offered on Delta's fleet of McDonnell Douglas MD-88 and MD-90 aircraft but has expanded to the remaining domestic fleet, as well as Delta Connection aircraft with a first class cabin. Delta has the largest fleet of Wi-Fi-equipped aircraft in the world. The airline introduced its first in-flight Wi-Fi on international routes to Tokyo from Los Angeles and Atlanta in March 2014, and stated its intent to offer the service on all transoceanic flight routes by the end of 2015. Even though Delta has announced the retirement of its 747 fleet, all Delta 747s are wifi-equipped and Delta is currently installing wifi on the 777 fleet.

In the 1960s audio programming was introduced where passengers wore headphones consisting of hollow tubes piping in music. These were installed in some Delta aircraft. Some early wide-bodied aircraft, including the Lockheed L-1011, Boeing 767-200, and 767-300 fleet, had movies projected on to the cabin bulkhead. Also during the late 1980s and early 1990s, CRT monitors over the aisles were added to the 757 fleet, making them the first narrowbody aircraft to feature video entertainment. The MD-90 introduced Delta's first IFE system with LCD monitors in 1995, and the 777 introduced Delta's first in-seat video system in 1999, initially using the Rockwell Collins Total Entertainment System. Delta's first all-digital IFE system with AVOD (Panasonic eFX) was first introduced in 2003 on Delta's former low-cost subsidiary, Song. The Rockwell Collins IFE system on the 777s was replaced by the Panasonic eFX system in 2007, followed by the Panasonic eX2 in 2011. The Panasonic eFX and eX2 systems are trademarked by Delta as Delta on Demand.

In the spring of 2010, Delta installed the Panasonic eFX AVOD system in Economy on six 767-300ERs that are used on routes that are 12 hours or longer. Delta also announced it would be installing AVOD in Economy class on all Boeing 767-300ER and 747 aircraft over the next 3 years.

On July 27, 2010, Delta announced that it would be the launch customer of the new eX2 AVOD system with the Eco 9i Integrated Smart Monitor, a new ultra-lightweight IFE system by Panasonic Avionics Corporation and Zodiac Seats U.S.. The systems have been installed on the entire 747-400 fleet as of October 2012, and are currently being installed on the 767-300ER fleet (except for the six aircraft previously retrofitted with the eFX system in 2010). A different version of the Integrated Smart Monitor developed by Panasonic Avionics Corporation and BE Aerospace is currently being installed on the Airbus A330 fleet. These seats will also be installed on the Boeing 757-300 and new Boeing 737-900ER fleet, and will replace the existing seats and monitors on the international Boeing 757-200 fleet.

In 2012, Delta began replacing the overhead CRT monitors on the pre-merger Delta 757-200 fleet with new LCD monitors. This was completed in late 2012.

The 767-400ER fleet initially featured LCDs over the aisles, but were replaced in 2009 by the Panasonic eFX AVOD system when the last of the 767-400ERs were converted from domestic to international use. CRT projectors were originally featured in economy class on Boeing 767–300s, with the international 767-300ERs also featuring ceiling-mounted CRT displays over the aisles, which have since replaced by LCD monitors, and are now in the process of being converted to the eFX2 AVOD system.

When Delta's ex-TWA ETOPS 757s were first delivered, they featured a system made by Sony Transcom (a former subsidiary of Sony now sold to Rockwell Collins) system that was factory installed for TWA. The system featured overhead drop-down LCD monitors similar to Delta's non-Transcon 737-800s and 757-300s. Delta replaced the Sony Transcom system with the Panasonic eFX system featuring in-seat video and AVOD at the same time as the new BusinessElite seats and slimline economy class seats were installed.

Audio and video are available on all aircraft except for the McDonnell Douglas MD-80 and MD-90, select Airbus A320, and Delta Connection aircraft. Boeing 777-200ER, 777-200LR, and 747 aircraft, along with those 767-300 and A330 aircraft that have completed cabin modifications, feature the Panasonic eX2 system. Compared to the older eFX system, this offers greater storage capacity, as well as lighter and larger personal video screens. Boeing 767-400ER aircraft, selected 757-200 aircraft, as well as the remaining internationally configured Boeing 767-300ER aircraft that have not completed cabin modifications, use the Panasonic eFX AVOD system. On these 767-300 aircraft, AVOD is available only in the Delta One class, while the system includes overhead LCD monitors and audio programming for passengers seated in the Economy cabin. The unmodified Airbus A330 aircraft feature the Panasonic 3000i AVOD system in all cabins. This system includes supplemental LCD monitors over the aisles for displaying the safety video and moving map.

Domestic Boeing 767–300s, Boeing 737–700s, as well as selected transcontinental Boeing 757–200s and selected Boeing 737–800s using the Panasonic eFX system, also feature live television via Dish Network in both first class and economy. Some Boeing 737-800s, as well as all Boeing 757–300s feature systems with drop-down LCD displays below the overhead bins.

All aircraft with AVOD feature Panasonic's iXplor moving map program. 737-800s with overhead video and the coach sections of 767-300ER aircraft with overhead video feature the Rockwell Collins Airshow moving map, which is often shown during takeoff and landing. Other aircraft formerly equipped with the Rockwell Collins Airshow moving map included the Lockheed L-1011-250 and -500, McDonnell Douglas MD-11, and Boeing 767-400ER and 777-200ER. The L-1011 and MD-11 fleet have since been retired, while the 767-400ER and 777-200ER have since had their Airshow systems replaced by the Panasonic iXplor system built into the eFX and eX2 AVOD systems.

Delta Sky Magazine and its online edition are published by MSP Communications in Minneapolis, Minnesota.

SkyMiles is the frequent flyer program for Delta Air Lines. As of September, 2017, one of the features of the program is that miles never expire.

Delta Air Lines' airport lounges are called Sky Clubs. Membership options include single visit passes and annual memberships that can be purchased with either money or miles. International business class passengers get free access. Membership can also be granted through top level Delta status or with the purchase of some American Express credit cards.

Features vary by location, but generally include free drinks (including alcoholic beverages), snacks and reading material. Wi-Fi is free for members and guests and is mostly provided in the USA by AT&T. Other benefits for Sky Club members include reciprocal lounge access with other SkyTeam members and Delta's other partners.

Originally, Delta's membership-based airport clubs were called Crown Room lounges, with Northwest's called WorldClubs.

On November 27, 2001, Delta Air Lines launched SkyBonus, a program aimed toward small-to-medium businesses spending between $5,000 and $500,000 annually on air travel. Businesses can earn points toward free travel and upgrades, as well as Sky Club memberships and SkyMiles Silver Medallion status. Points are earned on paid travel based on a variety of fare amount paid, booking code, and place origin or destination. While enrolled businesses are able to earn points toward free travel, the travelling passenger is still eligible to earn SkyMiles during his or her travel.

In early 2010, Delta Air Lines merged its SkyBonus program with Northwest's similar Biz Perks program.

In 2008, Delta Air Lines was given an award from the United States Environmental Protection Agency's Design for the Environment (DfE) program for their use of PreKote, a more environmentally friendly, non-hexavalent chromium surface pretreatment on its aircraft, replacing hazardous chemicals formerly used to improve paint adhesion and prevent corrosion. In addition, PreKote reduces water usage by two-thirds and reduces wastewater treatment.

PreKote is also saving money by reducing the time needed to paint each airplane. With time savings of eight to ten percent, it will save an estimated more than $1 million annually.

As part of the rebranding project, a safety video featuring a flight attendant showed up on YouTube in early 2008, getting over 1 million views and the attention of news outlets, specifically for the video's tone mixed with the serious safety message. The flight attendant, Katherine Lee, was dubbed "Deltalina" by a member of FlyerTalk for her resemblance to Angelina Jolie. Delta had considered several styles for its current safety video, including animation, before opting for a video presenting a flight attendant speaking to the audience. The video was filmed on a Boeing 757.

The following are major accidents and incidents that occurred on Delta mainline aircraft. For Northwest Airlines incidents, see Northwest Airlines accidents and incidents. For Delta Connection incidents, see Delta Connection incidents and accidents.

There have been over a dozen attempted hijackings that resulted in no injuries and the surrender of the often lone hijacker. These incidents are not included. The following are notable hijackings because of fatalities or success in forcing the aircraft to fly to another country: