New fleet of maritime patrol planes to be based at RAF Lossiemouth
David Cameron is also expected to cut an order for frigates with BAE Systems from 13 to eight.
The UK Government is to buy a new fleet of maritime patrol aircraft to be based at RAF Lossiemouth.
It is understood that nine Boeing P-8 Poseidon planes will be purchased as part of the Strategic Defence and Security Review.
The review has prompted much speculation about a possible response to the threat from Islamic State (IS) in the wake of the Paris attacks.
David Cameron will present the five-year National Security Strategy and Strategic Defence and Security review to the House of Commons on Monday.
It outlines how £178bn will be spent on equipment and support over the next ten years.
It is understood that shipbuilding along the River Clyde could be dealt a major blow in the review.
The Prime Minister had previously planned to order 13 Type 26 frigates from BAE Systems at Govan and Scotstoun but it is thought this will now be reduced to eight.
The site of RAF Lossiemouth was chosen for the new Boeing planes over an RAF base in Lincolnshire.
It comes after a decision in 2010 review to scrap Nimrod aircrafts which were previously based at nearby at RAF Kinloss.
Downing Street said the new maritime patrol aircraft would offer maritime surveillance, anti-submarine and anti-surface ship warfare capability, increasing further the protection of Britain's nuclear submarines and new aircraft carriers.
They will also provide maritime search and rescue and surveillance capabilities over land.
These roles require an aircraft that can carry torpedoes, as well as being fitted with a broad range of sensors, including radar and sonobuoys.
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