More than 140 well-paid manufacturing jobs are at risk at a titanium factory on the outskirts of Swansea.
Timet UK is consulting with unions and staff about 142 posts at its Waunarlwydd site, and a further 141 posts at its Birmingham plant.
The company makes titanium components like blades and fans for Rolls-Royce aircraft engines.
Rolls-Royce is cutting costs as aircraft manufacturers like Airbus reduce production in response to the coronavirus travel restrictions.
A spokeswoman for Timet UK confirmed it had entered into 45 days of consultation with union Unite and employees on 283 proposed redundancies in Waunarlwydd and Birmingham.
She said: "Although we are yet to understand the full impact of Covid-19 on the commercial aerospace industry, one thing for certain is that the pandemic has severely limited airline traffic, especially international flights.
"As the impact of the Covid-19 crisis and other macro-economic factors have weighed on the world, many of our customers have or intend to curtail or reduce their production.
"Due to the resulting reduction in orders, there is an immediate need to right-size our business to align with the demand for our products."
Some of the Timet UK workforce has already been furloughed.
The spokeswoman added: "The impact of Covid-19 on our product lines will be felt for a much longer period than the availability of the furlough scheme, and we need to find a more permanent solution to right-sizing our business in line with a significant reduction in volumes."
The Local Democracy Reporter Service understands that a second consultation meeting is due to take place today at the Waunarlwydd factory, which has a workforce of around 300, with efforts being made to reduce the number of compulsory redundancies.
One employee described Timet UK as a good employer, with terms and conditions which were good for the area.
"If they advertise for jobs, you get 5,000 people applying," he said. "It's high-tech stuff."
The employee said he felt the situation could only be turned around if the aviation sector picked up or the Government "chucks some money at it".
The Waunaylwydd factory will remain open - and the employee said it had been doing "really well" before the coronavirus outbreak.
Swansea councillor Chris Holley, who used to work at the plant as a maintenance fitter for 30 years, said he was "absolutely devastated" by the proposed redundancies.
"When I worked there we had reductions, but nothing like these figures," he said.
"I would hope the company says that workers will be given the opportunity to go back when there is an upturn."
He recalled that titanium medical devices, like replacement hip joints, were also made there.
"It was a very good company to work for," said Cllr Holley.
"We had a good rapport with the management and directors."
The factory used to be owned by Imperial Metals Industries (IMI) before American-owned Timet took it over.
Timet has production facilities in Europe, Asia and the US.
Cllr Mike Durke, whose Cockett patch includes Waunarlwydd, also described the potential job losses as devastating.
"My dad worked there when it was IMI," he said. "It was a great business. This is going to be difficult for so many people."
The Waunarlwydd plant was damaged by a fire in 2011.
Swansea West AM Julie James said: “Clearly this is a difficult time for all businesses in the area. I have spoken to the Minister for Economy, Ken Skates, about Timet and highlighted the critical importance of the company to Swansea.
“I know that his officials continue to work with Timet to discuss the future of operations in Waunarlwydd.”
Swansea West MP Geraint Davies said: “This is a hammer blow for Swansea and all the workers concerned at such a difficult time.
“It’s important they engage with the Welsh and UK Government to look at what support is available not just to furlough staff but to keep the business in the future.
“The aerospace industry is of critical importance in Wales - we have Airbus and those who cluster around the industry.”
