British Airways has had to rewrite its terminal five advertising campaign after The Sunday Times pointed out that it made incorrect claims about punctuality.

The promotion, which will soak up about 10% of BA’s £60m-a-year advertising budget, highlights time-keeping at T5, the airline’s new Heathrow base that opened amid scenes of chaos earlier this year.

The advertisements, which change daily to track performance, claimed that up to 90% of flights were “taking off within 15 minutes of the scheduled time”, a measure BA said was an industry standard.

Last week, however, the Civil Aviation Authority (CAA) confirmed the departure times were measured not at take-off, but when aircraft were pushed back from the terminal. At Heathrow, the CAA normally expects aircraft to spend at least 20 minutes taxiing before taking off. At busy times, the wait is normally much longer.

The mistake caused red faces at BA. “This was a genuine human error and we apologise if it was misleading,” said a spokesman.

A source at the airline said there had been a mix-up between BBH, the ad agency that devised the campaign and marketing staff.

“We are so annoyed because we knew we had to be spot-on with the wording, but someone at the agency changed it. We should have picked it up.”

The ads have now been changed to remove references to take-off times.

Virgin Atlantic, BA’s rival at Heathrow, is this week expected to complain to the Advertising Standards Authority about the campaign. Virgin claims that BA is making misleading claims about the time taken to clear security at T5 and that the period over which it measures the punctuality of flights avoids the evening peak.

The gaffes at T5 come at a sensitive time for BA. This week it will ask the US government to approve a tie-up with American Airlines.

Virgin is bitterly opposed to the deal.

Sir Richard Branson, Virgin’s founder, will this week write to John McCain and Barack Obama, the US presidential candidates, asking them to reject it.

“The competitive impact of BA/AA will be just as great, if not greater, this time as it was before,” Branson said.

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