The Stormont Executive has been asked to step in to assist workers at Co Down-based Collins Aerospace after the company announced 235 employees would not be returning to work at the end of their furlough period.
The news that around a quarter of the workforce were losing their jobs at the Kilkeel company could cost the local economy £10million a year.
Unite regional officer Kieran Ellison said the scale of the job losses would also mean uncertainty for many other workers and small businesses that depend on these employees for a livelihood.
"Unite is estimating that the Kilkeel job losses will cost the local economy £10million a year," Mr Ellison added said.
"While the likes of France and Germany have brought forward multibillion-pound strategies to safeguard jobs and skills in their aerospace sectors, the UK Government has made a patchwork of initiatives, whilst at the same time we are seeing a tsunami of job losses on its watch. Stormont also needs to step up in terms of support.
"As an immediate priority, we need to see the introduction of short-time working to enable continued employment, alongside a training programme to up-skill them for the future."
Collins Aerospace said it was continuing to experience difficulties due to Covid-19. It also forecast reduced business in future.
"This has forced us to take further actions to align with current and future business demands in an evolving environment," the company added.
"We have made the extremely difficult but necessary decision to commence a consultation process with the union and appointed staff representatives to discuss proposals to reduce headcount and make other operational changes in Kilkeel. This is a critical step to ensuring that Collins Aerospace emerges strong once this crisis is contained.
"The number of redundancies is subject to consultation, but the current proposals envisage 235 roles being made redundant."
Sinn Fein MP Chris Hazzard said the losses would come as a bitter blow to workers and their families.
"First and foremost, this is devastating for the workers, but it will also have a major impact on the local economy," he added.
"The company has exhausted a series of mitigation steps, including eliminating overtime, freezing recruitment and accessing the furlough job retention scheme.
"I have asked management to continue to proactively engage with workers at every stage of the process and offer retraining and up-skilling opportunities wherever possible for those workers affected."
SDLP MLA Sinead Bradley said the job losses at the company, which was the main sponsor of the Newcastle Festival of Flight last year, would be felt right across the local community.
"Employees have expressed their anxiety that they could be faced with unemployment by the end of October," she said.
"The retention of employment on this site is of critical importance to the economic prosperity of Kilkeel town and the surrounding areas.
"Immediate intervention from the Executive and Economy Minister Diane Dodds is needed.
"We can't afford to stand by and allow jobs critical to the local economy to disappear."
Approximately 1,100 jobs were lost in the aerospace sector in just one week in June when Bombardier in east Belfast and Portadown aeroplane seat manufacturer Thompson Aero announced redundancies.