A group of Conservative MPs have stated their intention to get a third runway included in the party's 2015 manifesto.
Transport minister Theresa Villiers ruled out the expansion at a London conference last week.
She admitted that there were differences of opinion on the third runway in the government, but that they were looking at all options for increasing aviation capacity "with the exception of a third runway at Heathrow".
But Conservative MPs who back a third runway are refusing to admit defeat. Three MPs separately mentioned their intention to secure support for the aviation policy in the next Conservative manifesto.
Sources at the Department for Transport responded that MPs will always be "lobbying" for the next manifesto, but that Villiers' speech clearly set out the government line on Heathrow.
Chancellor George Osborne signalled that the coalition could relax its stance for Gatwick or Stansted, but not for Heathrow.
Support in the City is growing for a Thames Estuary airport.
One senior executive, who works on large UK travel infrastructure projects, said that a third runway at Heathrow would be a short-sighted solution, compared to Boris Johnson's aviation option.
Another Tory politician added that senior ministers in the party want a third runway, but that it was unlikely to happen as part of a coalition.