London’s Gatwick Airport has announced it has begun preparing a planning application to obtain permission to bring its standby runway into regular use.

It said it had formally started the process by submitting a notice to the UK’s Planning Inspectorate.

It calls the project ‘Gatwick Airport Northern Runway’ and said that next month it would release its proposed approach.

Part of the plan, released last year, would see the maintenance and emergency runway – which runs parallel to the main runway – move marginally further north in order for it to comply with “all international safety requirements”.

The airport says that it would only be used for “smaller departing aircraft only”, and could potentially be brought into routine use by the mid 2020s.

The airport’s current planning agreement specifies that the standby runway can only be used when the main runway is closed for maintenance or emergencies, and will come to an end in 2019.

The application comes as debate continues over the addition of a third runway at London Heathrow. While the project has been approved by MPs it has not yet received planning permission, and continues to be criticised by environmental activists and many local residents.

It was also slammed last week by British Airways’ owner International Airlines Group (IAG), with CEO Willie Walsh accusing Heathrow of being on a “massive gravy train,” adding that “advance costs are spiralling out of control and total expansion costs are being covered up.” IAG argues that Heathrow will pass on some of the costs to its member airlines, who will then need to pass it on to passengers.

Other UK airports currently seeking to expand their operations include BirminghamLondon CityStansted and Bristol. Manchester is currently in the middle of a £1 billion expansion project.

Tim Norwood, Gatwick’s Chief Planning Officer, said: “As the biggest private investments in our region for many years, the start of the process to use our existing Northern Runway is a significant milestone.

“This project has the capacity to offer significant local economic benefits, new jobs and an exciting future for the region. As we take our plans forward, we are committed to working in partnership with our local communities, councils and partners to ensure we grow sustainably and present information in a clear and transparent way, including a more detailed stage of public consultation on the project next year.”

Members of the public can view updates on Gatwick’s application on the PINS website.

Earlier this month the airport released a £1.1 billion five-year investment plan that will see an extension to Pier 6 and other improvements.