Medway Council in Kent, UK, said 90% of airlines, including British Airways, Air France and Virgin Atlantic, are opposed to plans to build a new airport on the Thames Estuary.
The council will soon present a report to the city hall outlining the proposals made by the airlines, according to the BBC.
Due to the presence of large wildlife colonies in the estuary, the council and airlines are concerned the new airport will have a higher risk of bird strikes.
They are also concerned that the construction of the Thames Estuary Airport will lead to unemployment at Heathrow.
The airport, which would be situated on an island off the UK's south-east coast, is expected to cost £40bn (US$44bn) and is supported by the Mayor of London, Boris Johnson.