The outcome of a public inquiry into works at Heathrow has been delayed due to a debate over compensation for affected householders.
Bosses at the airport want to carry out taxiway alterations enabling more departures over Cranford , but their application was rejected by Hillingdon Council in 2014.
Heathrow appealed against that decision, and the findings of a public inquiry held last June are now being considered by Local Government Secretary Greg Clark and transport secretary Patrick McLoughlin , who between them must make the final ruling.
Heathrow had offered to fund soundproofing for properties experiencing a significant noise increase as a result of the change, and to cover the relocation costs where noise levels rise above 69dBLAeq - roughly equivalent to the volume of a vacuum cleaner.
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The transport and local government departments want to alter the conditions so households experiencing the greatest disturbance could opt for noise insulation, rather than help to relocate, should they prefer to stay put.
Stakeholders are now being asked whether they would accept these new conditions should the appeal be upheld, and they have been given until February 17 to respond.
35,000 extra flights per year over Cranford
There is no date set for a final decision but given those responses will have to be considered it is unlikely to be announced until several weeks after that deadline.
The taxiway works are needed to enable scheduled easterly take-offs from the northern runway, which were previously banned under the Cranford Agreement.
Without them, only a relatively small number of such departures have been possible since that 60-year-old verbal contract was scrapped by the government in 2009.
Should the work be approved, it would pave the way for roughly 35,000 extra flights a year over Cranford but no increase in the overall 480,000 flights a year at the airport.
Heathrow says the changes would make runway alternation more reliable and would be fairer on people living in areas like Windsor, Hounslow and Feltham , who would experience fewer planes overhead.
Councillors in Hillingdon opposed the planning application due to fears it would increase air pollution in the area, among other concerns.
Hillingdon and Hounslow councils, along with the Greater London Authority, all supported the case against Heathrow's proposals at the planning inquiry.
