Rolls-Royce has announced that around 4,600 jobs are being axed as the engineering giant looks to slash costs by another £400 million a year.
The group, which has a plant in Washington, said the bulk of these job cuts would affect the UK workforce and would be made over the next two years, with around a third expected by the end of 2018.
Rolls said the restructuring overhaul, which follows its announcement in January that it plans to slash its five operating businesses to three core units, will impact support functions and management, including within engineering.
It is not been specified where the job axe will fall across its UK sites.
But Rolls insisted it would honour a previous pledge not to impose compulsory redundancies on union-represented staff, including at its sites in Derby, Hucknall and Annesley.
This is the largest reduction in the company's headcount since 2001, when it announced plans to reduce 5,000 jobs, plus 1,000 contractors, which at the time was around 12% of the workforce.
Overall, Rolls has 55,000 employees worldwide, of whom 26,000 are in the UK, with 15,700 of those in Derby. It employs around 19,400 engineers.
Chief executive Warren East said: "We have made progress in improving our day-to-day operations and strengthening our leadership, and are now turning to reduce the complexity that often slows us down and leads to duplication of effort.
"It is never an easy decision to reduce our workforce, but we must create a commercial organisation that is as world-leading as our technologies."
Unite union assistant general secretary Steve Turner said: "This announcement will be deeply unsettling for Rolls-Royce workers and their families and could have a dire economic impact on local communities reliant on Roll-Royce jobs.
"There is a real danger that Rolls-Royce will cut too deep and too fast with these jobs cuts, which could ultimately damage the smooth running of the company and see vital skills and experience lost."
Rolls said its group-wide revamp will see it shift away from operating with "overlapping activities between individual business units and a large corporate centre".
It said: "We will be significantly reducing the size of our corporate centre to remove the complexity and duplication.
"A traditionally heavily centralised control culture will be replaced by empowered businesses, in a simpler, leaner structure with much clearer accountabilities."
The restructuring will cost it around £500 million - including redundancy costs - over the next three years, but will see it save £400 million every year by the end of 2020.
Recent annual figures showed Rolls-Royce returned to profit last year with a pre-tax surplus of £4.9 billion, thanks to a £2.6 billion accounting boost from the recent strengthening of the pound.
But it has been hit by technical issues with its engines, having uncovered durability problems with hundreds of its Package C Trent 1000 engines and earlier this month revealing further issues with a small number of its Package B Trent 1000 engines.