Looking to iron out problems at the fledgling terminal and ensure full baggage handling capacity, the airline claimed that some 120 long-haul flights would remain at Terminal 4 until at least June.
BA flyers may benefit from the delay as it gives the airline breathing space to restructure more gradually, averting the risk of further disruption and flight cancellation, but passengers with other airlines at Heathrow may find themselves affected by the new schedule.
Some 50 airlines will be affected by BA’s decision, with Heathrow’s second largest player bmi and many others planning to move into BA’s T4 slots once the flag carrier transfers its multiple long-haul services across.
BA chief executive Willie Walsh said: "It is only sensible to ensure that Terminal 5 is operating consistently at a high standard before the move begins. While a normal flight schedule has been operated at Terminal 5 since Tuesday, we want to ensure that customers can be confident of high service standards when additional flights are introduced."
Original plans had BA moving all its long-haul flights apart from Bangkok, Singapore and Sydney out of T4 by April 30th, with some 80,000 flyers expected to use the new terminal once all of the planned services are installed.
Passengers travelling out of the airport during this period should check with their airline or the airport to confirm which terminal their flight is due to depart from.