Please answer the following question: Information:  - Delta Air Lines, Inc. ("Delta") is a major American airline, with its headquarters and largest hub at HartsfieldJackson 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 Air France-KLM, Alitalia, Virgin Atlantic, and Virgin Australia. Regional service is operated under the brand name Delta Connection.  - SkyTeam is an airline alliance. Founded in June 2000, SkyTeam was the last of the three major airline alliances to be formed, the first two being Star Alliance and Oneworld. In terms of the number of passengers and the number of members, SkyTeam has grown and is now the second largest alliance in the world, second only to Star Alliance and ahead of Oneworld. , SkyTeam consists of 20 carriers from five continents and operates with the slogan "Caring more about you". It also operates a cargo alliance named SkyTeam Cargo, which partners ten carriers, all of them SkyTeam members. Its centralised management team, "SkyTeam Central", is based at the World Trade Center Schiphol Airport on the grounds of Amsterdam Airport Schiphol in Haarlemmermeer, Netherlands.  - Atlantic Coast Airlines was an airline based in the United States owned by Atlantic Coast Holdings , Inc. It operated as United Express for United Airlines and Delta Connection for Delta Air Lines . It was headquartered in the Dulles area of unincorporated Loudoun County , Virginia , United States . Previously it was headquartered in Reston , unincorporated Fairfax County . Before then , it was headquartered in Sterling , unincorporated Loudoun County .  - Virgin Atlantic, a trade name of Virgin Atlantic Airways Limited, is a British airline with its head office in Crawley, United Kingdom. The airline was established in 1984 as British Atlantic Airways, and was originally planned by its co-founders Randolph Fields and Alan Hellary to fly between London and the Falkland Islands. Soon after changing the name to Virgin Atlantic Airways, Fields sold his shares in the company after disagreements with Sir Richard Branson over the management of the company. The maiden flight from London Gatwick to Newark Liberty International Airport took place on 22 June 1984. The airline along with Virgin Holidays is controlled by a holding company, Virgin Atlantic Limited, which is 51% owned by the Virgin Group and 49% by Delta Air Lines. It is administratively separate from other Virgin-branded airlines.  - KLM Royal Dutch Airlines, legally "Koninklijke Luchtvaart Maatschappij N.V.", is the flag carrier airline of the Netherlands. KLM is headquartered in Amstelveen, with its hub at nearby Amsterdam Airport Schiphol. It is part of the Air FranceKLM group, and is a member of the SkyTeam airline alliance. KLM was founded in 1919; it is the oldest airline in the world still operating under its original name and had 32,505 employees . KLM operates scheduled passenger and cargo services to approximately 130 destinations.   - Air France (formally "Société Air France, S.A."), stylized as AIRFRANCE, is the French flag carrier headquartered in Tremblay-en-France, (north of Paris). It is a subsidiary of the Air FranceKLM Group and a founding member of the SkyTeam global airline alliance. As of 2013 Air France serves 36 destinations in France and operates worldwide scheduled passenger and cargo services to 168 destinations in 93 countries (including overseas departments and territories of France) and also carried 46,803,000 passengers in 2015. The airline's global hub is at Charles de Gaulle Airport with Orly Airport. Air France's corporate headquarters, previously in Montparnasse, Paris, are located on the grounds of Charles de Gaulle Airport, north of Paris.    After reading the paragraphs above, we are interested in knowing the entity with which 'atlantic coast airlines' exhibits the relationship of 'airline alliance'. Find the answer from the choices below.  Choices: - air france  - delta air lines  - skyteam  - star alliance
A:
star alliance