IMPACT says there is "still a lot to be done" before the Aer Lingus roster row is resolved.
Talks between management and trade union officials, aimed at ending the dispute, will resume at Dublin Airport this morning.
Cabin crew, who took part in a 24-hour work stoppage last Friday, are seeking a rota of five days on and three days off.
The airline says some progress is being made.
However, Michael Landers from IMPACT said that many issues still have to be addressed:
"Well I suppose what is positive is that Aer Lingus are talking to us about this because for weeks and months even years, they've been refusing to talk about it, so at least that is one positive move," he said.
"But there's still a lot to be done."