Most workers at Cork and Dublin airports face a vote on work practice changes as each grapples with massive declines in passenger numbers.
DAA, the State company responsible for both airports, is losing €1 million per day while Covid-19 restrictions continue to hit air travel.
Dalton Philips, DAA chief executive, told staff on Friday that unions representing the "vast majority" of working groups will be recommending agreed changes to staff.
As a result, unions including Mandate, Siptu and Fórsa will shortly begin balloting members in these areas.
Mr Philips noted that DAA has already opened applications for voluntary redundancy to these staff.
However, craft unions Unite and Connect, and security staff, represented by Siptu, have not yet reached agreement with DAA, so are not in a position to ballot members.
As a consequence, Mr Philips said DAA could not guarantee that those workers will continue to receive 80 per cent of their pay beyond August 29th, nor could it open applications for voluntary redundancy to staff in those areas.
DAA staff took a 20 per cent pay cut in April after air travel was largely grounded across Europe and the US, but the company pledged there would be no further reductions until August 29th.
The company says that workers who are balloting will continue to receive 80 per cent of their pay beyond that date.
Mr Philips confirmed that, assuming a yes vote in a ballot, DAA would continue to guarrantee staff 80 per cent of their pay while working to restore this to 100 per cent as quickly as possible.
Unite regional officer, Willie Quigley, who represents airport workers, expressed surprise at the DAA chief executive's remarks.
He explained that the union was not at the point where it could make a recommendation to DAA members, and thus could not hold a ballot.
“But we do intend to get to that point, we are trying to get to that point as soon as possible,” Mr Quigley said.
Dublin Airport handled 12,747 passengers on Thursday, down from around 100,000 normally at this time of year.
Just 1,465 people passed through Cork, which could have expected 10,000 passengers.