A monumental change to Europe’s busiest airport could mean an even bigger increase in London tourism. In a cabinet meeting Tuesday, Prime Minister Theresa May announced plans to build a third runway at Heathrow International Airport, making it the first major update the airport has seen in 70 years.

A Heathrow expansion could see more tourists in London, which in 2015 saw a record-breaking number of 31.5 million visitors, a 20% increase in five years, according to a May report from the Office for National Statistics. The report points to major sporting events like the Rugby World Cup and blockbuster exhibitions at the city’s museums and galleries as reasons for the increase in tourism. Additionally, figures show ever since the London 2012 Olympic and Paralympic Games, London has seen an increase in the number of visitors.

GettyImages-487951501 London at dusk with the London Eye, Jubilee Bridge and Houses Of Parliament. Photo: Getty Images

Of the 31 million total visitors, 18.6 million were international compared with 17.4 million in 2014. Domestic travel also experienced a huge boost with a record-breaking 13 million tourists from the UK. Separate research by independent forecaster Oxford Economics predicts London will welcome 35.6 million visitors by 2020, around the time Heathrow’s runway expansion is set to begin.

Heathrow’s planned expansion has been a hotly debated topic for decades, with many politicians — including Ex-PM David Cameron — striking down proposals. Yet supporters hailed the expansion as a way of creating more job and trade opportunities in the U.K.

“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,” the transportation secretary, Chris Grayling, said in a statement. “This isn’t just a great deal for business, it’s a great deal for passengers who will also benefit from access to more airlines, destinations and flights.”

GettyImages-617928370 British Airways planes taxi near Heathrow's Terminal 5 on Oct. 25, 2016 in London. Photo: Getty Images

Gatwick Airport — Heathrow’s lone competition and the second-busiest airport serving London — has one runway and is favored for expansion by some politicians including Mayor Sadiq Khan. Heathrow’s main European airports such as Amsterdam, Frankfurt and Paris all have more runways compared to London’s two.