General Electric will cut 369 jobs at its aircraft engine maintenance plant in South Wales.
GE consulted 1,400 employees at its site in Nantgarw, near Caerphilly, as the company is suffering from the decline in the number of air travel.
The company, which makes engines for Boeing and Airbus, blamed “the unprecedented impact of Covid-19”.
He said he remains focused on “preserving our ability to respond to the recovery in the industry.”
The announcement is in addition to 180 positions already lost on the site since the start of the coronavirus crisis by voluntary layoffs.
“Today’s news from GE is devastating news for Welsh workers, Welsh manufacturing and the Welsh economy,” said union leader Peter Hughes, regional secretary for Unite Wales.
“Our members at GE and their families will be extremely worried about their future today.
“Unite will fully support our members and will not budge from our position that compulsory layoffs should be excluded. ”
The union called on GE to halt its plans and “work with us to seek an urgent government sector agreement for aerospace that could save these jobs”.
Welsh Economy Minister Ken Skates said his officials would work to help those affected, but said there needed to be “immediate and radical action” on the part of the British government.
“We have already asked for action to be taken and I repeat it again today. Without action from the UK government, the future of the aerospace sector is in serious jeopardy, ”said Skates.
“Other central governments have acted quickly to protect their industries, the British government must do the same to safeguard a vital sector for our economy. ”
The British government has been asked for comments.
Pontypridd Labor MP Alex Davies-Jones and Senedd counterpart Mick Antoniw said the announcement was “absolutely devastating”.
They said it was “particularly distressing” that the majority of GE’s job cuts in the UK are falling on the Nantgarw site.
“These are highly skilled and well-paying jobs and they will be extremely difficult to replace,” they said.
It follows job cuts at British Airways in south Wales and the announcement of 1,435 layoffs at Airbus in Broughton, Flintshire.
Davies-Jones and Antoniw added: “The UK aerospace industry is in crisis and it is not acceptable for the British government to just shrug.
“We will continue to work with Unite the union and GE management locally to do everything we can to ensure as many jobs as possible are kept for the future and to support those who have lost their jobs in any way possible. “
Conservative business spokesperson in Senedd, Russell George, said, “If these reports are correct, then this will clearly be very disturbing news for employees at GE Maintenance’s Overhaul and Overhaul Facility. in south Wales, these are already very uncertain times, and it follows recent similar announcements from aeronautical companies operating in Wales. ”
He said his party would do “everything we can” to deal with the impact, including working with multiple parties with the Welsh government.
Delyth Jewell, member of South East Wales South East of Plaid Cymru, called on the Welsh government to consider investing in the “green economy”.
“I fear this is just the tip of the iceberg, we will see job losses in the weeks and months to come, which is why I urge the Welsh government to heed the call from Cymru pleaded for a pan-Welsh revival fund to help energize the sectors that are hardest hit by the crisis, “she said.
“To respond to this crisis, our communities need sustainable employment solutions.”