Heathrow Airport has promised to quadruple the number of homes eligible for noise insulation should it get a third runway, as it nearly tripled the amount of compensation available.
But anti-expansion campaigners called on the airport to make clear what long-suffering residents would be offered should it miss out on a new landing strip.
Heathrow last May proposed to expand its noise insulation scheme by increasing the compensation pot for homes, schools and other buildings under its flight paths from £30 million at present to £250m with a new runway.
On Monday (February 2), it announced that following consultation with local residents it was improving that sum to £700m and extending the offer to some 160,000 homes - including properties as far away as Windsor and Richmond.
Heathrow currently pays for soundproofing, including double glazing and loft insulation, at approximately 40,000 homes.
Under the new scheme, it would be available to all households within the 55 decibel Lden noise contour, with the worst affected getting the full cost paid and others getting up to £3,000 to pay for the work.
The compensation would be offered to people already affected by noise as well as those experiencing it for the first time with a third runway.
Heathrow chief executive John Holland-Kaye said: "We designed the new approach to expanding Heathrow to minimise noise to local residents, but we also need to mitigate the impact on those who are still affected.
"Today's announcement does that, and is based on the feedback we have received from local residents over the last few months; it will reduce the impact of noise, and treat local people fairly.
"Now we want to work with local communities to ensure that the opportunities from expansion – up to 40,000 new skilled jobs at Heathrow, 10,000 apprenticeships, tackling youth unemployment – benefit those who are most affected by expansion."
Heathrow vs Gatwick
Under the new scheme, more than 35,000 homes in Hounslow alone, including all those in Heston and Cranford, would be eligible for compensation.
The new offer was included in Heathrow's latest submission to the Airports Commission, which closes its public consultation on Tuesday.
The commission is due to make its final recommendations this summer about whether Heathrow, Gatwick or both should get an extra runway.
The Heathrow anti-expansion campaign group HACAN welcomed the new package, which it said would bring the airport in line with its main European competitors like Schiphol, Madrid, Charles de Gaulle and Frankfurt airports.
But it called on Heathrow to offer a more generous compensation package even if a third runway is ruled out - something the airport has yet to do.
HACAN chairman John Stewart said: "There is no doubt that this is much more generous than anything we have seen before and it brings Heathrow into line with other major European airports.
"But it does show how eager the airport is to get a new runway. It also suggests that residents have been short-changed in the past.
"Residents already living under the flight paths want to know today whether they will be offered improved insulation without a third runway because a new runway, whatever happens, is over 10 years away."
In December last year, Hounslow Council said the cost of insulating homes within the borough alone should a third runway be built would be £200 million.
In response to the news, Gatwick CEO Stewart Wingate said: "Heathrow should follow Gatwick's lead and offer to pay the council tax of people most affected if it's serious about compensating people for noise. Heathrow can't afford to do that of course as it already impacts more people than all the major European airports combined.
"Expand Heathrow and 320,000 new people will be affected by noise - a population the size of Coventry - compared to 18,000 people at Gatwick."