Prime Minister Theresa May’s government gave the green light to a 16 billion-pound ($20 billion) expansion of London’s crowded Heathrow airport, ending years of prevarication over what has become one of the most contentious issues in British politics.

The announcement Tuesday endorsed the conclusions of a state-sponsored commission that said last year Heathrow and not its rival Gatwick is the best candidate for growth amid a crunch in U.K. flight capacity. Construction of a new, third landing strip at Heathrow will allow the 70-year-old airport west of London to handle 135 million passengers a year, up from 75 million passengers now.

“The step that government is taking today is truly momentous,” Transport Secretary Chris Grayling said in a statement. “A new runway at Heathrow will improve connectivity in the U.K. itself and crucially boost our connections with the rest of the world, supporting exports, trade and job opportunities.”

A public consultation will now be held before final government proposals are put to Parliament in the winter of 2017-2018. May said last week that any ministers with “strongly held views” against expanding Heathrow would be free to continue to express their opposition, in a break from normal practice, though not in Parliament. Foreign Secretary Boris Johnson has been the most prominent of those critics.

While Heathrow remains Europe’s busiest airport, indecision over its expansion has seen that lead diminish in recent years as competitors including Frankfurt, Amsterdam and Paris Charles de Gaulle add flights on their multiple runways. Fast-growing hubs further east, including Dubai and Istanbul, are also grabbing a bigger share of the most lucrative long-haul transfer traffic.

Earlier Delays

May’s predecessor, David Cameron, put off a decision on Heathrow in December when he said more studies were needed on the environmental impact of a hub surrounded by the urban sprawl of west London and with flight paths over the center of the city. His earlier move to appoint an Airports Commission led by former Financial Services Authority Chairman Howard Davies to adjudicate on expansion had in turn avoided making the runway decision a potential vote loser in the 2015 general election.

While Davies shortlisted three proposals for adding capacity — including a second runway at Gatwick and an extension of one of the two existing runways at Heathrow — he concluded that the third-runway plan was superior. Carriers including British Airways also backed the model, arguing that expanding Gatwick would split flights between two similarly sized bases, making fewer routes viable than from a single super-hub with double the traffic.

Cameron had been hamstrung by a “no ifs, no buts” commitment not to expand Heathrow issued in the run-up to the 2010 election, as well as opposition to the plan among prominent figures in his own party, including lawmakers Zac Goldsmith, the conservative candidate in London’s last mayoral election, and Justine Greening, the education secretary, whose constituencies are under the flight-path.

Boris Island

Johnson was an outspoken critic of expanding Heathrow during his time as London mayor between 2008 and this year, proposing that Britain should instead build a completely new hub airport in the Thames estuary east of the capital. The model, dubbed “Boris Island,” was rejected outright by Davies.

Former Chancellor of the Exchequer George Osborne told lawmakers earlier this month that Britain’s June 23 vote to leave the European Union made it increasingly important for the nation to send a message that it is open for business by backing airport expansion.

“We can’t claim we are going to be trading with the rest of the world if we don’t have airports that planes can land on,” Osborne told Parliament’s Business Committee, adding that Britain has “dragged its heels” on adding new runway capacity in southeast England for the past 60 years.

Tony Blair’s Labour government offered support for expanding Heathrow in 2003 after a consultation the previous year, but the proposal became bogged down as environmentalists and local residents opposed the plan.

©2016 Bloomberg L.P.

This article was written by Christopher Jasper and Thomas Penny from Bloomberg and was legally licensed through the NewsCred publisher network.

Photo Credit: A computer generated image of what expansion at Heathrow might look like. The UK government has given its backing to a new runway at the airport. Heathrow