The support contract will see Raytheon provide maintenance, airworthiness, design and supplier management services, as well as modification and integration work that can give the Shadow fleet the capability to be upgraded in the future.
Shadow is a surveillance and reconnaissance aircraft that operates across the globe, and has been used regularly above battlefields in Iraq and Afghanistan.
"This £250 million investment will ensure the UK retains its position as a global leader in battlefield intelligence gathering for UK troops and our NATO allies. It is also great news for the economy through the safeguarding of 450 skilled jobs across the country, including 200 in North Wales, confirming the region as a UK centre of excellence for air support," said UK Defence Minister Stuart Andrew.
The UK is bringing a total of eight Shadow aircraft into service under commitments introduced in the 2015 Strategic Defence and Security Review.
"Defence Equipment & Support (DE&S) is proud to continue to work with our partners across industry to deliver world-class support to the RAF’s Shadow fleet. The continuing investment in support safeguards jobs and expertise which will provide safe and available aircraft in support of UK troops," said DE&S chief executive Sir Simon Bollom.