Parliamentary support for Heathrow expansion has grown in recent month, according to research commissioned by the airport.
Almost three of four MPs (74%) now say they back the third runway project, which has been chosen as the Government's preferred option for increasing capacity in South East England.
The poll of 130 MPs was conducted in October and November.
Its outcome suggests there has been a seven percentage-point increase in support among MPs since July and August, when a similar study was carried out.
The proportion of Conservative MPs in favour of expanding the west London hub has risen from 71% to 80%.
With 75% of Labour MPs also backing the scheme, Heathrow claims there would be "an overwhelming Parliamentary endorsement" if a House of Commons vote was held today.
Heathrow chief executive John Holland-Kaye said: "Heathrow expansion has more political support than ever before because MPs understand that a third Heathrow runway equips our country with the tools we need to thrive in the 21st century.
"This is why we have the confidence to invest in and to deliver Britain's new runway."
Several Cabinet ministers criticised the Government's October announcement that Heathrow, rather than Gatwick, was its preferred location for a new runway.
Foreign Secretary Boris Johnson described the project as "undeliverable" and claimed it was likely to be stopped, while Education Secretary Justine Greening said she was "extremely disappointed".
Zac Goldsmith quit as Tory MP for Richmond Park over the decision and lost the subsequent by-election in which he stood as an independent.
A draft National Policy Statement setting out why the Government believes a third runway is the best option for the UK is expected to be published early next year, when the public will be consulted on the proposals.