As speculation grows over the government's anticipated airport expansion decision next week, British Airways has said it would be "totally unacceptable" for carriers and passengers to bear the cost of construction.
Alex Cruz, chief executive of BA, told the British Air Transport Association that while a third runway at Heathrow Airport was "overwhelmingly" the obvious choice, it should "not be at any cost".
Cruz's airline is Heathrow's single biggest customer and he warned that should immediate prise rises come into effect, he would divert services to Dublin or Madrid - the homes of sister airlines within its parent International Airlines Group (IAG).
"The airport's shareholders should bear responsibility for the development costs, with no impact on passenger charges," Cruz said. He added that Heathrow's investors "do pretty well out of its monopoly hub status".
Cruz said the option of Gatwick getting the go-ahead for second runway would be "an astonishing move", though the latest speculation has pointed towards the possibility of a hybrid option - with the government weighing up a Gatwick first, Heathrow second plan.
The BA boss feels there isn't a business case for the Gatwick project - without sufficient demand from either customers or airlines.
Theresa May is expected to announce the decision as early as next Tuesday 18 October after a series of delays, including David Cameron's resignation following the Brexit vote, put airport expansion in the south east on hold.
The Airports Commission recommended Heathrow as its "clear and unanimous" choice in July last year, though Gatwick has questioned its forecasts as being inaccurate and out of date.
In September, Gatwick's chief executive Stewart Wingate said the airport had flown 42m passengers in the last year - undermining the commission's findings, which hadn't predicted it to pass that mark for another 14 years.