Airline began as holding company called United Aircraft and Transport Company for these airlines: Boeing Air Transport, Varney Air Lines, Pacific Air Transport and National Air Transport. Name changed to United Air Lines in 1931. Merged with Capital Airlines in 1961. In 1985, United purchased Pan American Airways entire Pacific Division. In 1994, United's pilots, machinists, bag handlers and non-contract employees agreed to an Employee Stock Ownership Plan (ESOP), acquiring 55% of company stock. UAL Corporation filed for Chapter 11 bankruptcy protection in December 2002 and the ESOP was terminated. The board of directors of both Continental and UAL Corporation's. United Airlines reached an agreement to combine operations on May 2, 2010. On October 1, 2010, UAL Corporation completed its merger with Continental Airlines and changed its name to United Continental Holdings, Inc. On March 3, 2012, Continental and United merged their passanger service systems.