The expansion, which has been a major point of contention in the UK for many years, got the green light from the British parliament in June 2018.
Challenges from environmental campaigners were dismissed by the High Court in May, one of the country's highest legal bodies, clearing one of the final obstacles to the project.
The new architectural designs reveal the first visualization of what the airport might look like when the expansion is completed in 2050, well beyond the anticipated opening of the third runway.
The plans include a "third space" concept for a new terminal, which will "integrate public spaces and the airport, providing hybrid outdoor-indoor spaces," the airport explained.
They also reveal the proposed position of the third runway, which is expected to be developed to the north-west of the airport, where it will traverse the M25 -- London's outer traffic beltway -- and engulf surrounding communities. More than 750 homes are slated to be demolished, including the entire village of Longford.
The designs suggest that a new runway bridge will be built over the M25, akin to a similar structure at Paris's Charles de Gaulle airport, presenting huge engineering challenges to builders and potential disruption to surrounding traffic.
The plans detail compensation policies for residents directly affected by the expansion, including those in a so-called Compulsory Purchase Zone, who will be required to sell their property, and other affected areas. They also outline the airport's noise insulation policy, and its measures to combat air pollution and climate change.
The airport has opened a 12-and-a-half-week public consultation on the newly unveiled plans. It invites the public to have their say on a number of issues, including the proposed layout and development schedule.
It will also seek feedback on how the airport plans to mitigate impacts on the surrounding communities and environment. This includes a 6.5-hour ban on scheduled night flights, the creation of a low-emission zone and the introduction of a vehicle access charge, similar to that seen in central London.
"Heathrow's expansion is a project of huge national and local significance, and it is critical to our country's economic growth," Emma Gilthorpe, the airport's executive director for expansion, said in a statement ahead of the consultation launch. "An expanded hub airport will allow the country to access more of the world, create thousands of jobs locally and nationally and it will open up new trading routes."
But she insisted that the airport wanted to deliver the project in the "fairest and most sustainable way" possible.
"Expansion must not come at any cost," she said. "That is why we have been working with partners at the airport, in local communities and in government to ensure our plans show how we can grow sustainably and responsibly -- with environmental considerations at the heart of expansion."
Following the conclusion of the consultation, the airport will submit its final proposal in 2020 to the Planning Inspectorate, a governmental executive agency responsible for determining key planning issues.
The decision on whether to grant permission will then be made by the government's minister for housing, communities and local government.
The plans have drawn sharp criticism from many environmental campaigners, who lashed out at elected members of parliament (MPs) who agreed to the expansion.
"The only answer to Heathrow expansion plans is a big, fat NO," Sian Berry, co-leader of the Green Party, wrote on Twitter. "More planes will trash the planet and trash Londoners' transport capacity, air quality and our mental health. Shame on every MP who voted to get it to this stage."
Caroline Russell, a Green Party London councilor, added: "Parliament has recently declared a climate emergency. That should over ride the third runway vote. MPs need to pick a side. Do they back climate emergency action or Heathrow expansion?"
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