Aerospace specialist Bombardier is aiming for a return to work at its Belfast sites on May 4, with some operations potentially resuming as early as next week.
The Canadian-owned plane manufacturer yesterday confirmed it has informed staff of the plan after consultations with trade unions.
The company said it "may begin work progressively in some areas and functions" from April 27.
The decision has been criticised by People Before Profit MLA Gerry Carroll who said: "I cannot see how supplying aircraft parts is an essential service during this crisis, and I think we should be made aware if and why a Stormont Minister officially deemed Bombardier workers as essential.
"If Bombardier workers were not deemed essential, then the Executive must urgently act to prevent this return to work.
"Workers are already speaking out and have been in contact with me to raise concerns.
"Their lives should not be risked for business interests.
"As a priority, the Executive, and the Irish and British Governments should rebuke those businesses which are attempting to reopen before lockdown is ended, and move to shut down any attempt to return to work."
In a statement, Bombardier confirmed it had already tested measures in some areas of its business.
"We recently issued an employee communication confirming that we have taken a decision, in consultation with our trade unions, to extend our current furlough period, targeting a return to work at our Belfast sites on Monday, May 4, 2020," a spokesperson said.
"We also communicated that we may begin work progressively in some areas and functions from April 27, 2020 to support crucial deliveries, particularly to external customers.
"The health and safety of our employees remain our top priority.
"During this furlough period, we have carried out a thorough review of all our facilities, in collaboration with our trade unions and the Health and Safety Executive, to put the best measures in place and ensure we meet the latest government social distancing and workplace health and safety guidelines. Indeed, we have already piloted some measures in certain areas.
"On their return, employees will experience quite significant changes in some working areas and practices to ensure their safety.
"They may also be required to work alternative patterns to facilitate safer working.
"Management will support employees to adapt to this new way of working, but we will of course continue to communicate with them regularly before their return.
"Where possible, we will also continue to maximise working-from-home opportunities."
The Department for the Economy published a list of 'priority sectors' on Friday, but described it as advisory, stating that Northern Ireland companies would be able to make their own decisions.
A leading employment law specialist said there was no legal reason why a company could not call on employees to return to the workplace if all appropriate health and safety measures had been taken.
"In real terms there is no reason why a company can't phase employees back in, as long as they have completed all relevant risk assessments and consulted with trade unions," said Louise McAloon, who heads the largest employment law practice in Northern Ireland at Worthington's Solicitors.
"There are options of furlough in rotation to ensure all workers are treated equally and if social distancing measures are maintained, there's no legal reason not to open."