Defence giant BAE Systems said up to 371 jobs will go as the group slows production of its Typhoon jet fighters.
The vast majority of the job losses will affect its workforce in Samlesbury, Lancashire, although some roles will also be impacted in its Typhoon final assembly production team in Warton.
It employs 13,000 across the two sites.
BAE said it hoped to find opportunities elsewhere in the business for staff in an effort to limit the number of compulsory redundancies.
The blow comes as BAE is having to stretch out its Typhoon production line.
It secured a deal to supply 28 Typhoon aircraft for the Kuwait Air Force in September, with deliveries from the Italian Typhoon final assembly line set to start around the end of the decade.
The group is also in talks with Saudi Arabia to try to secure further Typhoon purchases, but discussions are making slow progress.
Engine-maker Rolls-Royce announced it would be “streamlining” its senior management next year.
The firm has around 2,000 staff in that category.
It is not clear how many are at risk, but the cuts will not be limited to its UK operations.
The announcement forms part of a broader restructuring programme, which Rolls-Royce chief executive Warren East hopes will save the firm around £150 million to £200m a year.
“The next few years are going to be important in laying the foundations for our long-term profitable growth,” he said.
The engine-maker downgraded its profits forecast for next year again.