is poised to be massively expanded, upping its capacity to the dismay of campaigners.

Transport Secretary Heidi Alexander has “set out a path to approving” Gatwick Airport’s expansion project, a Government source told PA Media. This comes after the Planning Inspectorate initially rejected the West Sussex airport’s application to bring its emergency runway into routine use.

The Planning Inspectorate then recommended Ms Alexander should give the project the go-ahead if adjustments are made on issues such as the proportion of passengers who travel to and from the airport by public transport, and noise mitigation. An official decision is expected later today.

Gatwick airport's expansion plan involves bringing its emergency runway into routine use. Here we answer 14 key questions about the project.

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How many runways does Gatwick have?

It has one conventional runway, and one standby runway.

What is the standby runway used for?

It is mostly used for aircraft to taxi to and from terminals, but is also used when the main runway is closed for emergencies or maintenance.

Why does Gatwick want to expand?

It is the UK's second busiest airport and one of the busiest single-runway airports in the . Spare slots at peak periods are scarce and the runway is heavily utilised, meaning disruption can have a severe knock-on effect.

What must happen to the standby runway for it to be brought into routine use?

It must be moved 12 metres to the north – away from the main runway – to meet strict aviation safety rules.

What else does the plan involve?

Remodelling and replacing existing taxiways, which connect runways to terminals, hangars and other facilities, extending both terminals, and installing new aircraft gates.

How about transport?

Gatwick says it would pay for road connections to both terminals to be enhanced, creating fly-overs which separate local traffic from vehicles travelling to or from the airport. A £250 million upgrade of the airport's railway station was completed in November 2023.

What would the standby runway be used for?

Departures of narrow-bodied planes such as Airbus A320s and Boeing 737s.

What would be the effect on Gatwick's flight capacity?

The airport could handle approximately 386,000 flights annually, an increase of about 100,000 from current figures.

What about the yearly passenger count?

The numbers could surge from around 45 million to a staggering 75 million by the late 2030s.

What is the estimated cost of the project?

Gatwick has projected a hefty £2.2 billion price tag for the plan.

Who will foot the bill?

The airport has assured that the project will be privately financed, promising to cover the costs without increasing charges to airlines.

When is the new runway expected to open?

Gatwick has labelled the scheme as "shovel ready", indicating that construction could commence this year. It anticipates the new runway to be functional by the end of the decade.

Who owns Gatwick airport?

The French firm Vinci and investment fund Global Infrastructure Partners are the owners.

Will Heathrow's third runway proposal impact Gatwick?

The Government has shown its support for Heathrow's expansion plan. However, it may take several years before construction on a third runway at the west London airport begins, and Gatwick is keen to enhance its own capacity.

What do environmental campaigners say?

They are not happy. Finlay Asher, aerospace engineer and member of Safe Landing said: "The expansion plans at Gatwick are a flight in the wrong direction. Rather than outdated airport terminals for conventional aircraft, if a new runway is opened, it should be for zero-carbon aircraft only."

“British aviation’s future lies in innovation, not expansion. Electric or hydrogen aircraft are our ticket to greener, cleaner and quieter flights. They can reduce carbon, air and noise pollution for communities living under flight paths. We have a golden opportunity to back British manufacturing and create jobs developing sustainable technology that we can sell worldwide. But we need airports like Gatwick to play their part, by providing a clear route to market.”

"If the UK doubles down on conventional growth, we’ll build too much airport capacity compared to the level of flying eventually possible. This will lead to stranded assets, with investors losing out and job losses for aviation workers in a devastating “boom-and-bust” scenario.”

Alethea Warrington, head of aviation at climate charity Possible, added: “Giving the green light to yet another airport expansion is as economically clueless as it is environmentally destructive.

“Expanding airports won’t support the UK economy or raise living standards for ordinary people. More flights will just mean frequent flyers going on even more holidays, taking even more tourism spend overseas and further increasing the UK’s massive £40bn tourism deficit.

“Instead of wasting time, money and emissions on polluting projects which will harm our climate and our economy, the government should get on with things that actually make people’s lives better: rolling out more renewable energy, insulating homes and investing in clean, affordable trains and buses.”