Atlantic Southeast Airlines (ASA) is an American regional airline based in Atlanta, Georgia. The airline was founded in 1979 as Atlantic Southeast Airlines, Inc. It is a wholly owned subsidiary of Delta Air Lines, operating regional flights.

The company was established in 1979 by a group of investors led by Robert F. Munro, who had previously founded and operated Gulfstream International Airlines in Florida. The group was looking to expand the regional airline market in the southeastern United States and they saw the potential to create a profitable business by connecting smaller cities that lacked service from major carriers.

Their first aircraft was a single-engine Cessna 402, which was used to launch the airline's first scheduled passenger service between Columbus, Georgia and Macon, Georgia in August 1979. By 1981, ASA had grown to include a fleet of seven aircraft and was providing service to nine cities.

Throughout the 1980s, ASA continued to expand its operations. The airline's fleet grew to include larger aircraft, such as the Fairchild Swearingen Metroliner, and operations were extended to include markets in the Caribbean and Central America. By 1989, the airline was operating a fleet of 18 aircraft and serving 26 cities in the Southeast.

In the 1990s, ASA began to experience rapid growth. The airline added additional aircraft to its fleet, and by the end of the decade, had a total of 80 aircraft. In 1996, ASA was acquired by Delta Air Lines, becoming a wholly owned subsidiary. As a result of the acquisition, the airline was able to launch new routes to cities in the Northeast and Midwest, and to increase its presence in existing markets.

In 2001, ASA became the first regional airline in the United States to receive the Federal Aviation Administration's Diamond Award for Maintenance Excellence. This award recognized the airline's commitment to safety and maintenance.

In the 2000s, ASA continued to expand its route network. In 2003, the airline became the first regional carrier to offer service to London, England. The airline also launched new routes to Mexico and Canada.

In 2005, ASA experienced its first major incident when a flight from Atlanta to Birmingham, Alabama, crashed shortly after takeoff due to a failure of the left engine. The crash resulted in the deaths of three passengers and the injury of two crew members.

In 2011, ASA was the focus of a federal investigation which revealed a number of safety violations. As a result of the investigation, the airline was fined $2 million and faced a number of other penalties.

Today, ASA operates more than 800 daily flights to over 150 destinations throughout the United States, Canada, Mexico, and the Caribbean. The airline has a fleet of more than 100 aircraft, including regional jets and turboprops.

Overall, Atlantic Southeast Airlines has grown from a small regional carrier to a major airline. The airline has experienced a number of important milestones throughout its history, including its acquisition by Delta, its first international service, and the implementation of a number of safety initiatives. Despite the occasional incident, ASA continues to provide reliable and safe service to its customers.