Up to 500 workers could be made redundant by Portadown-based Thompson Aero Seating.
The Chinese-owned firm, which makes aircraft seats, employs about 1,300 people across four factories in Northern Ireland.
The trade union Unite said a redundancy consultation process has begun.
Manufacturing NI has described the news as a "devastating blow" and said more redundancies were likely within the sector.
Unite said that an adjustment to the government's furlough scheme could help save jobs.
Unite said Thompson's have a major order which needs to be completed in June so it will not be possible to furlough ahead of that deadline.
Regional Secretary Jackie Pollock said: "At present, workers must be furloughed before June 10th to receive support under the scheme; however, this is simply not possible where companies have contractual obligations for orders which are due immediately after this date.
"This is the case in Thompsons Aero Seating and means five hundred workers now face the prospect of redundancy rather than support under the furlough scheme."
The potential redundancies are in addition to 330 job losses announced in March.
Stephen Kelly, from Manufacturing NI, said similar announcements could be made in the coming weeks due to the closure of the furlough scheme June and local employment laws.
"Just this week we reported that half of manufacturing firms believe they may have to lose one third of their workforce and one in eight firms may not survive this year," he said.
"The manufacturing sector is resilient and many will find a way out of the current crisis, but they need the support of the [Northern Ireland] executive through financial intervention, smart and brave policy making and quick decisions to give them a fighting chance."