Plans to move flight paths in and out of major British airports away from built up areas have been launched by the firm that manages UK air traffic.
Nats says the proposals would mean a reduction in noise for many
National Air Traffic Services says its plans would cut by 20% the number of people affected by noise from departing planes flying below 4,000ft (1,219m).
Airports including Heathrow, Stansted, Luton and London City may be affected.
The new flight paths could be in place by spring 2009 if the Civil Aviation Authority gives Nats the go-ahead.
Nats says it will hold a 13-week consultation with people and organisations from across five affected areas - Cambridgeshire, Suffolk and north-east Essex; the Chilterns and Luton; east Hertfordshire and west Essex; west and north-west London, and east London and south-east Essex.
More than 3,000 people and organisations will be consulted, including MPs, local councils, green groups, airlines and businesses.
The proposals include:
Reducing congestion over Brookmans Park in Hertfordshire caused by converging departure routes from Heathrow, Luton, London City and Northolt airports
Relocating and separating the holding facilities - or stacks - for Luton and Stansted
Introducing what are called continuous descent approaches where aircraft stay higher for longer, reducing fuel burn and noise, for Stansted's easterly runway
Operations director Ian Hall said: "All these airports have grown considerably in the past 20 years. London City has grown from virtually nothing since the early 1990s - and we have simply accommodated this growth within the existing airspace infrastructure.
"Just like bottlenecks on roads, increased air traffic causes congestion in the airways meaning delay and extra fuel burn - and that has an impact on the environment."
But he added that the plans - the first major overhaul in UK air routes for decades - would not mean the number of flights would be reduced.
"We also have to accommodate growth forecast under existing government policy so now is the right time to overhaul the airspace fundamentally to ensure we maintain our high safety standards, reduce delays and minimise the effect on the environment," he said.
Jonathan Astill, head of air space management for Nats, said the proposals were about "taking a real look at the route network".
"In doing that we're trying to reduce the number of people that are overflown at the lower levels," he said.
He added that the aim was also to "make it possible for aircraft to climb to the higher levels quicker so that they get away from the airports, they create less noise, they burn less fuel and therefore they create less emission".
But Martin Peachey, who chairs Stop Stansted Expansion's noise committee, warned the proposal would mean there would be both winners and losers.
"While we welcome moves to reduce noise impacts, such as proposals for greater use of continuous descent approaches, there will clearly be losers as well as winners across the region since the noise has to go somewhere," he said.
"The new routes mean that aircraft would be flying over communities that have previously enjoyed relative tranquillity where overflying will make a greater impact because of the absence of other background noise.
"The question we are asking is why the holding stacks aren't being put to the east, over the sea. Given that most flights arrive from the east and the south, this would have far less impact on the population as a whole."
In response, Nats said the sea was too far away as holds needed to be an "optimal" distance from the airport "so that air traffic control can integrate the flow of aircraft in an orderly manner".