It comes as the Cabinet considers the findings of an expert report into the sale of the government's 25 per cent stake.
Labour Deputy Joe Costello says commitments must be given on the Heathrow slots and job security for Aer Lingus staff.
He added the future of airports like Shannon and Cork also needs to be taken into account before any deal can go ahead.
Meanwhile, SIPTU – which represents half of the workforce at Aer Lingus – says it will “vigorously oppose” the takeover – unless IAG provides commitments that it won't seek redundancies.
Divisional Organiser Owen Reidy says the union isn't being unreasonable.
