Question: Southeastern Airlines was acquired by a carrier of what regional airline that operates short and medium-haul routes?

Context paragraphs:
Air Wisconsin: Air Wisconsin Airlines is a regional airline based at Appleton International Airport in the town of Greenville, Wisconsin, United States, near Appleton.  Air Wisconsin is the largest privately held regional airline in the United States.  It currently operates regional jet flights as American Eagle under contract to American Airlines via a code sharing agreement, serving cities in the U.S. and Canada with hubs at Boston Logan International Airport (BOS), Charlotte Douglas International Airport (CLT), Philadelphia International Airport (PHL) and Ronald Reagan Washington National Airport (DCA) .  Air Wisconsin previously operated United Express service on behalf of United Airlines followed by US Airways Express service on behalf of US Airways prior to becoming an American Eagle regional air carrier.  The company has announced it will once again partner with United Airlines as a United Express code sharing air carrier with primary hubs to be located at Chicago O'Hare International Airport (ORD) and Washington Dulles International Airport (IAD) beginning in September 2017 and will be "exclusively operating" as United Express by March 2018.

Delta Connection: Delta Connection is a regional airline brand name for Delta Air Lines, under which a number of individually owned regional airlines operate short- and medium-haul routes.  Delta's lone wholly owned regional airline, Endeavor Air, also resides under the Delta Connection banner.  Mainline carriers often use regional airlines to operate services in order to increase frequency, serve routes that would not sustain larger aircraft, or for other competitive reasons.

Air Nostrum: Air Nostrum, Líneas Aéreas del Mediterráneo, S.A., also known as Iberia Regional, is a regional airline based in Valencia, Spain.  Air Nostrum is an independent carrier which operates as a franchisee of Iberia Airlines and Binter Canarias.  Iberia Regional franchise is a regional partner of Iberia and an affiliate member of the Oneworld airline alliance.  Air Nostrum operates 91 domestic and international routes to 51 destinations, and charter flights.  Its main base is Valencia Airport, with hubs at Barcelona Airport and Madrid-Barajas Airport.

China Airlines: China Airlines (CAL) () () is the flag carrier and largest airline of the Republic of China (Taiwan).  It is headquartered in Taoyuan International Airport and has 12,607 regular employees.  China Airlines operates over 1,400 flights weekly to 118 airports in 115 cities (including codeshare) across Asia, Europe, North America and Oceania.  The cargo division operates 91 pure freighter flights weekly.  The carrier was, in 2013, the 29th and 10th largest airline in the world in terms of passenger revenue per kilometer (RPK) and freight RPK, respectively.  China Airlines has three airline subsidiaries: Mandarin Airlines operates flights to domestic and low-demand regional destinations; China Airlines Cargo, a member of Skyteam Cargo, operates a fleet of freighter aircraft and manages its parent airline's cargo-hold capacity; Tigerair Taiwan is a low-cost carrier established by China Airlines and Singaporean airline group Tigerair Holdings and is wholly owned by China Airlines Group.

Iberia Express: Iberia Express is a Spanish low-cost airline owned by Iberia, which operates short- and medium-haul routes from its parent airline's hub at Adolfo Suárez Madrid–Barajas Airport, providing feeder flights onto Iberia's long-haul network.

Regional Airline Association: The Regional Airline Association (RAA) is a business association founded in 1975 that represents 31 North American regional airlines and 280 associate, non-airline members.  This includes manufacturers of products and services supporting the regional airline industry.  The RAA is the collective bargaining voice for its members' interests and lobbies on their behalf before the United States Congress, Department of Transportation, Federal Aviation Administration and other federal agencies.  The RAA represents the financial and economic interests of regional airline employers and regional airline support industry employers.  The Regional Airline Association does not represent financial or economic interest of airline employees, either union or other.  The RAA is headquartered in Washington DC.

Cathay Dragon: Hong Kong Dragon Airlines Ltd (Chinese: 港龍航空公司), operating brand as Cathay Dragon (Chinese: 國泰港龍航空) and previously as Dragonair, is a Hong Kong-based international regional airline, with its corporate headquarters, Cathay Dragon House, and main hub at Hong Kong International Airport.  As of 30 October 2013, the airline operates a scheduled passenger network to 44 destinations in 13 countries and territories across Asia.  Additionally, the airline has 3 codeshares on routes which are served by partner airlines.  It has an all Airbus fleet of 41 aircraft, consisting of A320s, A321s and A330s. Cathay Dragon is a wholly owned subsidiary of Hong Kong's flag carrier, Cathay Pacific, and is an affiliate member of the Oneworld airline alliance.  The airline was founded on May 24, 1985 by Chao Kuang Piu, the airline's present honorary chairman.  Its maiden flight departed Hong Kong for Kota Kinabalu, Malaysia after being granted an air operator's certificate (AOC) by the Hong Kong Government in July 1985.  In 2010, Dragonair, together with its parent, Cathay Pacific, operated over 138,000 flights, carried nearly 27 million passengers and over 1.80 billion kg of cargo and mail.

TAP Express: TAP Express (Transportes Aéreos Portugueses or TAP for short) is a Portuguese regional airline brand name for TAP Portugal which operate short- and medium-haul routes.  TAP Portugal's lone wholly owned regional airline, Portugália Airlines, operates under the TAP Express banner.  White Airways, an airline owned by Omni Aviation, also operates regular flights for TAP Express using 9 ATR 72 turboprops.  Its head office is on the grounds of Lisbon Portela Airport in Lisbon.

Southeastern Airlines: Southeastern Airlines was a regional airline that was acquired by Atlantic Southeast Airlines, a Delta Connection carrier, on April 1, 1983.  It was formed in 1982 by Atlanta entrepreneur Michael J. Brady, who had formerly been head of Eastern Metro Express, a feeder for Eastern Airlines.

SkyWest Airlines: SkyWest Airlines is a North American airline owned by SkyWest, Inc. and headquartered in St. George, Utah, U.S..  According to the Airlines for America definitions, SkyWest is a North American major airline.  SkyWest however, operates on a regional airline level and is a member of the Regional Airline Association.  SkyWest Airlines flies to 238 cities, in 45 states; Washington, D.C., six Canadian provinces and five cities in Mexico.  The airline serves as a feeder airline, operating under contract with various major carriers.  It flies as SkyWest Airlines in a partnership with Alaska Airlines, as United Express on behalf of United Airlines, as American Eagle on behalf of American Airlines, and as Delta Connection on behalf of Delta Air Lines.  SkyWest also provides ground handling services for airports across the United States.

Supporting paragraphs: Southeastern Airlines Delta Connection
Answer: Delta Connection