The former Labour transport minister made clear his hostility to Heathrow expansion in his mayoral manifesto in March. “I understand how urgently our city’s economy needs additional aviation capacity in order to stay competitive with other major world cities,” he said. But he added: “This must be done without further breaching limits on pollution.”

He said he would “make the case for a second runway at Gatwick as the cheapest, greenest and most viable option presented by the Airports Commission” and “oppose a third runway at Heathrow”, adding: “If the government chooses to pursue this option, [I would] continue to call for a new runway at Gatwick as a more viable, cheaper and easier to build alternative”.

However, Abta’s head of public affairs Stephen D’Alfonso said the fact that London had a Labour mayor could give the government more licence to advocate a third runway.

Writing for TTG (Opinion, page 27), D’Alfonso said: “It might now be easier for a Conservative government in Westminster to deliver a decision for Heathrow in the face of opposition from a Labour mayor than it might have been if the second most powerful elected Conservative politician [Zac Goldsmith] was leading that opposition.”

Khan himself has flip-flopped in his support for airport expansion. As transport minister under Gordon Brown, he led Labour’s support for a third runway at Heathrow but U-turned last summer after pitching for the mayoral candidacy.

He raised eyebrows this week after signalling his aim to appoint former transport secretary and chair of the National Infrastructure Commission, Lord Adonis, to govern transport in London. Adonis has previously also been an advocate of a third runway.

A government decision on airport expansion is due this summer.