Aircraft seating manufacturer Thompson Aero Seating in Portadown is cutting up to 500 jobs as aviation is hit by falling demand due to Covid-19.
And a manufacturing boss has warned that many more job losses are likely in the sector.
Chinese-owned Thompson Aero had already cut around 350 agency roles at the outset of the pandemic and lockdown.
It will be left with around 720 employees after the latest reduction in headcount - a 40% cut to its current 1,220 workforce. Thompson Aero specialises in business class seating for major airlines like Aer Lingus, American Airlines and Qantas.
But the company said it was now facing market challenges, as many major airlines have grounded their fleets since lockdown.
However, it also suffered a £27.7m loss in 2018, according to company accounts published in October, down from a £10.7m pre-tax profit a year earlier.
A spokeswoman said: "The global airline and aviation industries are experiencing extreme challenges as a result of Covid-19 - unprecedented developments, which have significantly impacted and reduced global demand for aircraft seating.
"As a result of these major market challenges, Thompson Aero Seating is announcing a redundancy programme with a proposed reduction of up to 500 jobs, which represents a 40% reduction and will bring the company's headcount back to the numbers employed in the business as recently as 2018."
The company said it is now holding a consultation with employees and their union reps, with the jobs to go over the next few months.
However, Kieran Ellison, Unite regional officer for Thompson Aero, said the union is seeking for workers to obtain furlough instead of being made redundant.
He added: "If these workers can be furloughed instead of being made redundant it offers some hope to safeguard jobs until demand in the aerospace sector improves."
The scheme closes to new applicant companies on June 10.
Stephen Kelly, the chief executive of trade group Manufacturing NI, said more job losses were likely in the sector.
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 Executive through financial intervention, smart and brave policy making and quick decisions to give them a fighting chance."
Upper Bann DUP MP Carla Lockhart said the job losses were also a "devastating blow" for the supply chain across Northern Ireland.
She said: "The Government must look more strategically at the aerospace sector given the impact of Covid-19."