London's Heathrow Airport is planning to build a third runway and carry out a multi-billion-pound expansion of two of its five terminals, its chief executive has confirmed.

Thomas Woldbye said on Wednesday the airport wants to increase capacity at Terminal 2 and Terminal 5 and change the layout of its runways in the short term. He said it also intends to formally seek permission this summer to build a third runway, all in the name of keeping up with surging demand.

"This privately funded program will upgrade existing infrastructure while laying the groundwork for a third runway, boosting UK investment and economic growth, with tangible benefits felt this year," he said.

Woldbye explained that the expansion of the United Kingdom capital's main airport, which handled 83.9 million passengers last year and around 1,300 landings and take-offs each day, will be financed by the private sector and not by the British government.

He laid out the plan while visiting a British Steel plant in the northern town of Scunthorpe, where he signed an agreement to use the company's products during the construction work.

The UK's finance minister, Chancellor of the Exchequer Rachel Reeves, has already said Heathrow's expansion is "badly needed", and could create 100,000 jobs while boosting the country's economy.

But critics have said a third runway and the additional capacity will lead to more flights, more emissions from burned aviation fuel, and less chance of the UK meeting its climate goals.

Woldbye insisted the expansion will target efficiencies, sustainable practices, and green alternatives and there will not necessarily be more noise and pollution.

"This project can only go ahead if we meet the rules on noise, air quality, and carbon ... it's as simple as that," he said. "I want to assure you that we are committed to listening and working with our local communities to provide them with the certainty they deserve, ending years of doubt."

After Heathrow Airport submits its plan for a third runway this summer, a formal planning process will begin that could take around a year and a half to complete. Appeals to UK courts by opponents of the expansion could take another year and a half and construction of the third runway would likely take at least seven years after that, meaning aircraft are unlikely to be using the new runway before 2035.

Heathrow believes a third runway would increase its total number of flights annually from 480,000 to 720,000, and its passenger numbers from 84 million a year to 140 million.

But the construction of a third runway would mean some rivers would need to be diverted, and part of the M25 London orbital motorway would need to go underground. Several hundred homes would also be forcibly purchased and demolished.