SIPTU has called on Aer Lingus management to give further details of its cost savings plans.
The union particularly wants the airline to specify how much money the company hopes to save by cutting overheads.
At a meeting of shop stewards today, SIPTU members raised questions about the cutbacks while the airline was growing and proving to be profitable.
Meanwhile, Ryanair has further extended its deadline for Aer Lingus shareholders to accept a €1.48bn takeover bid for the airline until 22 December.
Yesterday a second deadline for acceptance of the Ryanair bid expired.
Ryanair said this morning that shareholders holding almost five million shares had accepted its offer, representing just under 1% of the total shares in Aer Lingus.
The bid is widely expected to fail given intense opposition from major shareholders, including the Government with 25% and current and former Aer Lingus staff with 12.6%.
Ryanair shares had gained 2c to stand at €9.65 in Dublin this morning, while Aer Lingus was down one to €2.73.
