British Airways postponed the transfer of most long-haul flights to Heathrow's problem-plagued Terminal 5 to ensure it can handle the extra passengers and baggage.
The delay puts the carrier more than a month behind schedule. It had planned to switch almost all of its long haul flights from Terminal 4 on April 30, but now said it will be unable to do that until atleast June 5.
"We are making this decision in the interests of customers," said British Airways chief executive Willie Walsh, adding that June 5 was the earliest the switch would occur. "Though Terminal 5 is now working well, we need to have confidence that good service can be maintained when the terminal is handling larger numbers of customers."
The opening of Terminal 5 has been a public relations disaster for British Airways, which had hoped the new building would end to frequent complaints about delays and overcrowding at the airport, Europe's busiest.
The carrier has canceled hundreds of flights since the $8.6 billion terminal opened on March 27 and a high-tech baggage routing system broke down.
At one point, more than 15,000 pieces of luggage went missing. Walsh said Friday that three-quarters of those have now been returned.
British Airways has said the problems have cost it some $32 million in lost revenue and compensation through March.
The delay by British Airways could lead to compensation claims against Heathrow's operator BAA.
The carriers that had expected to move into the terminal space vacated by British Airways, including Alitalia SpA, Air Transat and Aeroflot, must now wait.