Fleet service, the beginning of the end was when they bought too many 747's, 25 plus 8 more ordered by Najeeb Halaby. They were flown during the oil crisis, sometimes with only a handful of passengers. The next blow came in 1980 when they overpaid for National Airlines. It would have been much cheaper to begin a domestic network themselves. They also would have avoided many union problems had they not integrated National Airlines into the largely veteran Pan Am pilot base.
As for the LHR routes, these were sold in 1990 and transferred in April-1991, not 1988. The original agreement:
23 October 1990 - Pan Am announced it would sell its flagship routes between the U.S. and London (Heathrow) to United Airlines and two jumbo jets for about $400 million. The routes were London (Heathrow) to Los Angeles, New York, San Francisco, Seattle, and Washington, DC; London to continental European cities including Amsterdam, Berlin, Brussels, Hamburg, Helsinki, Munich and Oslo. Pan Am kept routes between London and Detroit and Miami (to be flown to Gatwick). United also would aquire Pan Am's route between Washington (Dulles) and Paris as part of the deal as well as agreeing to pay up to $100 million worth of Pan Am tickets should Pan Am stop flying. The acquisition was to include two Boeing 747-200 widebody aircraft built for long-range flight. A marketing agreement was to bring United's MileagePlus frequent-flyer program together with WorldPass.
Pan Am was the leading trans-Atlantic carrier with 14.1% of the market. TWA had 11.8%, British Airways PLC had 11.1%, Lufthansa had 6.8%, American Airlines Inc. had 5.5%, KLM Royal Dutch Airlines had 5.2%, Air France had 3.6% and Delta Air Lines Inc. had 3.5%.
11 November 1990 - Trans World Airlines proposed buying Pan Am Corp. for $450 million in cash and securities. The deal was contingent on Pan Am backing out of the U.S.-London routes sold to United Airlines.
24 December 1990 - Pan Am Corp. received a $20 million cash infusion from United Airlines in an advance payment as part of a larger $400 million sale agreement for U.S.-London routes and other assets.
08 January 1991 - Pan Am Corp. filed for Chapter 11 Bankruptcy Court protection in New York. Reasons cited were Pan Am 103, skyrocketing fuel prices since the August 2 Iraqi invasion of Kuwait, and the recession.
10 January 1991 - U.S. Bankruptcy Court approved Pan Am Corp.'s sale of key London routes to United Airlines and a related financing package that will give Pan Am $150 million. Final approval is dependent on British approval.
11 March 1991 - Britain's Department of Transport approves the transfer of Pan Am's London (Heathrow) routes to United.
British Airways holds the greatest share of the British-American market, with 39%. Pan Am had 15%, TWA 14% and Virgin Atlantic 7%.
01 April 1991 - United Airlines and Northwest Airlines receive emergency approval from the U.S. Department of Transportation to begin temporary flights between Miami and London (Heathrow) and Detroit and London (Gatwick), respectively. Northwest later drops plans to fly the Detroit to London route citing that it can't make money serving the route only until May 23, when Pan Am reclaims the route.
03 April 1991 - Pan Am transfers its London-Heathrow authority to United Airlines and also enters into a major marketing agreement with United.
07 May 1991 - Pan Am announced it will resume service on the Miami-London route on May 18 and the Detroit-London route on May 23. Pan Am will fly to London-Gatwick. Pan Am leased the Miami route to United Airlines on April 3 to allow United to offer Miami-London (Heathrow) service while reviewing the possibility of further cooperation with Pan Am.