Plans to introduce a third runway to Heathrow could see the busy M25 motorway moved into a tunnel. The consultation document includes proposals for a 3,200 metre runway, the end of which would pass over the top of the motorway.
MPs are expected to vote on the plans later this year. The construction would see the road shifted 150 metres west and lowered by seven metres to make room for the raised runway. The runway itself would also be cut by 300 metres from the originally proposed 3,500m.
The estimated cost of this proposal would be £14 billion - £2.8 billion less than originally suggested. Airlines have expressed concerns that landing charges would be increased to help pay for the new runway, but Heathrow insists the cost would remain close to today's £22 per passenger.
The plan set out has work beginning in 2021, with the new runway open by 2025. Heathrow says the motorway would remain partially open throughout, easing congestion.
Emma Gilthorpe, Heathrow's executive director of expansion, said the airport wanted to hear the public's views on the matter. "We need feedback to help deliver this opportunity responsibly and to create a long-term legacy both at a local and national level," she said.
John Stewart, chairman of anti-Heathrow expansion group Hacan, said: "We welcome the chance to shape the new flight paths rather than have them imposed.
"If a third runway is ever given the go-ahead we want the best possible deal for residents."