The full legal name of the company is United Airlines, Inc., which operates as a major American airline headquartered at the Willis Tower in Chicago, Illinois. It is a wholly-owned subsidiary of United Airlines Holdings, Inc. (formerly known as United Continental Holdings). The airline has a complex corporate history, beginning as "United Air Lines" in the late 1920s through the consolidation of several smaller mail carriers under the United Aircraft and Transport Corporation. A pivotal moment in its identity occurred in 2010 when it merged with Continental Airlines; while the "United" name was kept for the combined company, the current logo (the blue globe) was actually inherited from Continental. As a founding member of the Star Alliance, the largest global airline partnership, United Airlines, Inc. remains one of the "Big Three" legacy carriers in the United States. In everyday business and on the stock exchange (NASDAQ: UAL), it is simply referred to as United, but all formal contracts, safety regulations, and legal filings use the full "United Airlines, Inc." designation to distinguish the operating carrier from its parent holding company.