The outcome of a public inquiry which could have a big impact on Heathrow's neighbours is unlikely to be known until next year.
Bosses at the airport appealed after their application to carry out taxiway alterations enabling more departures over Cranford was refused by Hillingdon Council last year.
A public inquiry began in June this year but the report is not due to be sent to the local government minister Greg Clark until November 9.
It is not known when he will make his ruling but decisions typically take around 14 weeks, according to the Planning Inspectorate, meaning it could be well into next year before the outcome is known.
If approved, the taxiway work would spell the end of a 60-year-old verbal contract at the airport, known as the Cranford Agreement, in practice.
That unwritten agreement, which prevented easterly take-offs from the northern runway, was scrapped by the Government in 2009.
But only a relatively small number of departures over Cranford have since been possible as new taxiways are needed to enable regular scheduled departures.
Heathrow claims the move would make runway alternation more reliable and reduce the noise experienced by those in other areas like Windsor, Hounslow and Feltham, which are currently overflown more because so few planes take off over Cranford.
But councillors in Hillingdon opposed the application last year, largely due to concerns over increased air pollution.
Hillingdon and Hounslow Councils, along with the Greater London Authority, all supported the case against Heathrow's proposals at the recent planning inquiry.
Ending the Cranford Agreement in practice would mean roughly 35,000 extra flights a year over the area but no increase in the overall 480,000 flights a year at the airport.