No, Delta Air Lines and United Airlines are two completely separate and competing companies, though they are both major "legacy" carriers based in the United States. They belong to different global airline alliances: Delta is a founding member of SkyTeam, while United is a founding member of the Star Alliance. Their hubs and primary operations are also distinct; Delta is headquartered in Atlanta and has major hubs in cities like Detroit, Minneapolis, and Seattle, whereas United is headquartered in Chicago and has major hubs in Houston, Newark, and San Francisco. They have completely different fleet structures, loyalty programs (Delta SkyMiles vs. United MileagePlus), and corporate cultures. While both airlines are part of the "Big Three" in the U.S. (alongside American Airlines), they are fierce rivals on many domestic and international routes. It is a common misconception among casual travelers that all "legacy" airlines are merged or part of the same parent company, but Delta and United remain independent entities with their own stock symbols (DAL and UAL) on the New York Stock Exchange.