British Airways has conceded Terminal 5 cannot handle the carrier’s full volume of traffic.

The airline completed its first week of operating a full schedule from the terminal as Travel Weekly went to press, but provoked fury among rivals by postponing completion of its move to Terminal 5 until June or possibly even as late as October.

BA had originally planned to complete the move at the end of April. It has so far moved only domestic and European flights, which carry less than half of BA passengers.

More than 50 airlines are due to move into the space vacated by BA. Chief executive Willie Walsh described the delay as being in passengers’ interests, saying: “We need to have confidence service can be maintained when the terminal is handling larger numbers.”

But BMI chief executive Nigel Turner accused BA of “mismanagement” and said: “BAA and BA have shown a total disregard for other airlines and passengers.”

A senior corporate travel executive blamed fundamental flaws in British Airways’ attitude to passengers for the troubled opening. Hogg Robinson Group industry affairs director Mike Platt said: “Terminal 5 is like a Formula 1 car with two-star petrol in it. It is a perfect storm of poor infrastructure and over-optimistic assumptions.”

“The terminal has been built around passengers who check in online and bring very little baggage. But a lot of leisure travellers have bags and are used to conventional airports.”

BA had still to return 5,000 bags to clients this week. On Tuesday the debacle cost two of its senior managers their jobs – director of operations Gareth Kirkwood and customer services director David Noyes.

However, the carrier has been keen to praise the trade for its help in dealing with the fallout. A spokesman said: “We want to thank the trade for all the work put in. Now we need to keep relations strong. We know we need to re-double our efforts.”