AMERICAN submarine-hunting planes will fly out of a Scottish RAF base after a £62m investment at the site.

The US is developing and refurbishing facilities at Lossiemouth - soon to be home to Britain’s own fleet of patrol aircraft - as Nato steps up its monitoring of the North Atlantic.

The new facility at the Moray base is expected to be completed in 2020 to coincide with the initial operation of the UK’s new P-8A Poseidon maritime patrol aircraft.

These new planes - versions of the Boeing 737s operated by airlines like Ryanair - are a belated replacement for Nimrods which used to monitor the Scotland Iceland gap.

This stretch of open seas was a key battleground in the Cold War and is increasingly active as Russia once again flexes its naval muscles.

The main job of the new Poseidons, however, will be to protect Trident submarines based at Faslane and Britain’s new aircraft carriers from Russian hunter-killers and other potential threats.

The Ministry of Defence has welcomed the planned contribution to the base from the US, which is set to cover a number of works at the air station. These will include contributing towards refurbishment of the runway, additional aircraft parking and hangar space and accommodation to meet US requirements, it is understood.

The US has previously operated from RAF Lossiemouth but it is understood the improvements do not mean there will be a permanent US basing at the site.

Defence chiefs believe the RAF P8 fleet and the US submarine hunters will play a key role in keeping the UK and its allies safe.

An MoD spokeswoman said: “We are investing £3 billion in our nine-strong, new P-8A Poseidon fleet over the next decade.

“The contribution of $80 million from the US to the home of our submarine-hunters at RAF Lossiemouth will support our partnership with our closest ally and will help us be more efficient by sharing improved facilities, and will see us patrol the seas together to have more eyes and ears on any aggressors.”

The MoD announced that Lossiemouth, which is home to three units of Typhoon fighter jets, would be to be the future home of its new Poseidon fleet. The US has also announced a $150m investment in another RAF base, Lakenheath in East Anglia, where it will base new F35A fighters.