UAL, Inc. and United Air Lines bond certificates 1978

Transition to the UAL name (holding corp for United Air Lines at the time) Fantastic aviation cert at an affordable price. The stock-sized piece has a vignette of the winged god, Mercury holding a winged wheel and a caduceus. Blue pieces are $1000 bond denominations while the orange is for various amounts. Issued and cancelled. Dated 1978.

United Airlines, Inc., commonly referred to as "United", is an American major airline headquartered in Chicago, Illinois. It is the world's largest airline when measured by number of destinations served. In the late 1920s, just prior to the use of the United Airlines name, The Boeing Company, currently one of the world's largest aircraft manufacturers, operated a predecessor airline.

United operates out of nine airline hubs in the continental United States, Guam, and Japan. George Bush Intercontinental Airport in Houston is United's largest passenger carrying hub handling 16.6 million passengers annually while Chicago-O'Hare is its largest hub in terms of daily departures. The company employs over 88,500 people while maintaining its headquarters in Chicago's Willis Tower (formerly known as Sears Tower). Through the airline's parent company, United Continental Holdings, it is publicly traded under NYSE: UAL.

United's main competitors in its domestic market are Delta Air Lines, American Airlines, and Southwest Airlines. United is using Continental's air operator's certificate and it surrendered its original certificate when the merger closed.

United Airlines traces its roots to Varney Air Lines air mail service of Walter Varney, who also founded Varney Speed Lines, from which Continental Airlines had originated. Founded in Boise, Idaho in 1926, the carrier flew the first Contract Air Mail flight in the U.S. on April 6, 1926, marking the first scheduled airline service in the country's history. In 1927, aviation pioneer William Boeing founded his own airline, Boeing Air Transport to operate the San Francisco to Chicago air mail route, and began buying other airmail carriers including Varney Airlines. In 1929, Boeing merged his company with Pratt & Whitney to form the United Aircraft and Transport Corporation (UATC).

In 1933, United began operating the Boeing 247, the first all-metal airliner. It was able to fly a transcontinental flight in 20 hours, making it significantly faster than its predecessors. After passage of the Air Mail Act in 1934, UATC separated into United Aircraft (the future United Technologies), the Boeing Airplane Company and United Air Lines.

After World War II, United gained from a boom in customer demand for air travel, with its revenue per passenger-miles jumping five-fold in the 1950s, and continued growth occurring through the next two decades. United merged with Capital Airlines in 1961 and regained its position as the United States' largest airline. In 1968, the company reorganized, creating UAL Corporation, with United Airlines as a wholly owned subsidiary. In 1970, the UAL Corporation acquired Western International Hotels, and its name was later changed to Westin Hotel Company. The 1970s also saw economic turmoil, resulting in "stagflation" and labor unrest. The 1978 Airline Deregulation Act, resulting in industry shakeups, further added to the carrier's difficulties in a loss-making period.

In 1985, United expanded dramatically by purchasing Pan Am's entire Pacific Division, giving it a prime Asian hub at Tokyo's Narita International Airport, and in 1991 purchased routes to London Heathrow Airport from ailing Pan Am, making it one of two US carriers permitted exclusive access to Heathrow under Bermuda II until "open skies" took effect in 2008 (American Airlines being the other, after it purchased TWA's Heathrow landing slots).

The aftermath of the Gulf War and increased competition from low-cost carriers led to losses in 1991 and 1992. 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 in exchange for 15–25% salary concessions, making the carrier the largest employee-owned corporation in the world. The carrier also launched a low-cost subsidiary in 1994, Shuttle by United a high frequency, west coast-based operation, in an attempt to compete with low-cost carriers; the subsidiary remained in operation until 2001.

During the September 11, 2001 attacks, two of the four airliners hijacked and crashed by al-Qaeda members were United Airlines aircraft. United Airlines Flight 175 was flown into the south World Trade Center tower; United Airlines Flight 93 was crashed in a field in Pennsylvania after the passengers fought back against the hijackers. After attempts to secure additional capital failed, UAL Corporation filed for Chapter 11 bankruptcy protection in December 2002 and the ESOP was terminated.

United's bankruptcy operations resulted in furloughing thousands of workers, closing all U.S. city ticket offices, cancelling several existing and planned routes, downsizing its Miami operations, closing maintenance bases, and fleet reductions. The carrier also negotiated cost cuts with employees, suppliers, and contractors, and terminated feeder contracts with United Express carriers Atlantic Coast Airlines and Air Wisconsin.

In 2005, United announced it had raised US$3 billion in financing to exit bankruptcy and filed its Plan of Reorganization, as announced, on September 7, 2005. In late 2006, Continental Airlines participated in preliminary merger discussions with United. On April 16, 2010, United resumed merger talks with Continental Airlines.  The board of directors of both Continental and UAL Corporation's United Airlines reached an agreement to combine operations on May 2, 2010.

The Continental–United merger was approved by the European Commission in July 2010 and by the US Justice Department on August 27, 2010. On September 17, 2010, United's shareholders approved the merger deal with Continental Airlines. Both carriers planned to begin merging operations in 2011 to form the world's biggest carrier. On October 1, 2010, UAL Corporation completed its merger with Continental Airlines and changed its name to United Continental Holdings, Inc.