Management at Dublin and Cork airports may cut up to one-thousand jobs in a bid to address significant financial losses.
Workers were told today that the cuts are necessary as lower passenger numbers are expected in 2021.
The DAA says it needs to take action quickly and the details of a voluntary severance scheme will be revealed next week.
It says business at Irish airports is currently down 99% when compared with the same time last year, and the outlook for the rest of 2020 remains bleak.
SIPTU Sector Organiser Neil McGowan said "We will insist that any workers leaving the company as a result of redundancy must do so on a strictly voluntary and agreed basis and our focus will be to ensure that as many jobs possible are maintained in Dublin and Cork Airports."
Mr. McGowan says "we've been in contact with staff in the hour's following the announcement today and people are very worried."
"I don't think anybody is blind to the difficulties that the entire aviation industry across the world finds themselves in. It is a very worrying time."