LONDON — Northrop Grumman has signed a nine-year extension to a deal with the British Royal Air Force (RAF) to support its fleet of Sentry E-3D airborne early warning aircraft.

The contract award has yet to be announced by the UK arm of Northrop Grumman, but news the deal had been signed emerged when Cohort, one of the industry subcontractors in what is known as the Sentry Whole Life Support Program (WLSP), unexpectedly released the information earlier this week.

The company said in a statement it "is pleased to announce that its subsidiary MASS has been awarded a nine-year extension to its managed IT service contract for the Sentry at RAF Waddington."

Northrop Grumman UK declined to comment.

The company has been providing maintenance and modification services for the British Sentry fleet since it was awarded the original support deal in 2005.

At the time, Northrop Grumman said that over the 20-year life of the program, the potential value of the deal could be worth in excess of £665 million (US $813 million).

It remains Northrop Grumman’s biggest single contract in the UK.

AAR Corp. and Cobham Aviation Services are also partners with MASS and Northrop Grumman in the program. BAE was part of the original industrial lineup but has since dropped out.

In its release, Cohort valued its element of the final nine years of the current 20-year program at around £12 million.

The scope of the work being undertaken by its MASS subsidiary now includes replacement of the maintenance, repair and overhaul software and adds an enterprise performance management solution, the company said.

A Northrop Grumman executive earlier this year said the final part of the 20-year deal also involved the contractors in providing higher operational availability rates than currently required for the six-strong fleet.

The Sentry aircraft were originally scheduled to be retired from RAF service in 2025, but that date was pushed back 10 years in last November’s Strategic Defence and Security Review.

A much needed update of the platform is expected to get underway by around 2020. An original scheme, known as Project Eagle, was abandoned in 2009 due to defense budget cuts.