British MPs are set Monday to approve plans to build a third runway at London Heathrow, Europe's busiest airport, after decades of acrimonious debate.
Prime Minister Theresa May's government agreed to the £14 billion (15.9 billion euros, $18.5 billion) plan earlier this month, saying it would provide a major boost to the economy.
Many MPs, particularly those representing London and south-east England, are strongly critical, fearing the noise and pollution impact on a densely populated area.
Foreign Secretary Boris Johnson once pledged to lie in front of bulldozers to stop construction, but he will be abroad for the vote.
Transport Secretary Chris Grayling said he was "cautiously optimistic" of securing approval for the plan, which officials say could create up to 114,000 local jobs by 2030.
"This is a momentous vote that has been 50 years in the making and represents the biggest transport decision in a generation," he said.
"At stake are thousands of new jobs and the country's ability to compete on an international stage and win new global trade."
Grayling said the project would be funded by the private sector, adding that the government would work with Heathrow's operator to ensure costs are not passed on to airlines.
British Airways owner IAG has expressed concerns about higher landing charges for what it said is already the most expensive hub airport in the world.
Grayling also pledged that the plan could be delivered without breaking Britain's existing commitments on climate change, and has also offered reassurance for locals.
However Doug Parr, policy director for environmental campaign group Greenpeace UK, said: "A vote for a new Heathrow runway is a vote for more climate change, more air pollution, and more noise."
A junior trade minister and London MP, Greg Hands, quit the government last week to vote against the plan -- and criticised Johnson for dodging Monday's late-night vote.
"I wouldn't want to be abroad...#commitments," Hands wrote in a Twitter message.
May has in principle demanded all her Conservative MPs back the plan, but she supported Johnson's trip abroad, saying he would be the "living embodiment of global Britain".
It was not clear exactly where Johnson was, with the Foreign Office citing security concerns.
The main opposition Labour party is against Heathrow's expansion but has given its MPs a free vote.
Many are expected to back the government and the proposal has trade union support.
If parliament gives approval, Heathrow will publish detailed proposals for the new runway which will be subject to further public consultation and planning consent.
Local authorities could raise legal challenges, although it hopes to start construction in 2021.
© 2018 AFP