1990: Buys Pan Am's routes to London Heathrow to complement its 1985 purchase of the failing carrier's Pacific division. First transatlantic service, between Frankfurt and both Chicago and Washington, in May. Places a record $22 billion aircraft order.

April 1991: First service to Heathrow.

1992: United loses $957 million as chief executive Stephen Wolf threatens a sell-off and demands concessions

1993: Wolf changes livery to grey, blue and red, prompting pilot protests. In November it takes the first Airbus A320, which represents a major break with the carrier's former owner, Boeing.

1994: Wolf sets up an ambitious Employee Stock Ownership Plan (ESOP). This gives pilots and machinists unions 55% stake in parent United in return for wage and work-rule concessions. Former Chrysler executive Gerry Greenwald takes over as Wolf departs. In October, Shuttle by United is launched as a low-fare West Coast "airline within an airline".

1997: United joins with Lufthansa, Air Canada, SAS and Thai and later with Varig to form the Star Alliance. United ends its 12-year-old "Friendly Skies" slogan and replaces it with "Rising".

1999: Union pressure forces United president John Edwardson to resign as Greenwald's successor. James Goodwin, a 32-year veteran, is named to step up and succeed Greenwald

April 2000: Pilots operate a slowdown in protest at lack of progress in contract talks

May 2000: United proposes acquisition of US Airways Group for $4.3 billion.

September 2000: United, ALPA sign landmark contract after a summer of alleged pilot slowdowns and sick outs. Pact gives pilots record wages to make up for concessions in the now-expired ESOP.

July 2001: US Airways takeover collapses in face of antitrust objections.

September 2001:United traffic and performance declines and then plunges after 11 September terrorism.

November 2001: Shuttle is terminated.

Source: Airline Business