IAG has offered concessions to regulators in order to win European competition approval for its planned acquisition of Aer Lingus, the European Commission said.
European authorities said they have extended the deadline for their decision on whether to allow the bid to proceed until July 15, from the original July 1.
That timing means the decision, including details of any concessions that are agreed with IAG - such as allowing rivals greater access to routes or to landing slots including those at Heathrow Airport - will be known before Aer Lingus shareholders are due to meet on July 16 for an extraordinary general meeting to cast their votes on the IAG offer.
The Government owns 25pc of Aer Lingus and has already said it is backing the sale, but the airline's biggest shareholder, Ryanair, with almost 30pc of the stock, has not yet said how it plans to vote at the EGM.
IAG's bid to buy Aer Lingus is driven in part because it plans to expand lucrative transatlantic services from Dublin Airport where there is spare capacity, unlike London's Heathrow where its biggest unit, British Airways, is based.
IAG submitted its concessions on Wednesday, the EU competition authority said on its website, without providing details.
A spokesman for IAG said it will not discuss possible concessions until negotiations with the Commission conclude.
"IAG's engagement with the Commission is ongoing, and it would be inappropriate to comment further at this stage," he said.
Aer Lingus was not immediately available to comment.
Sources told Reuters last week that the Commission was unlikely to approve the stake buy without concessions from IAG to allay competition concerns.
The relative speed of the current competition review has probably been helped by the fact that some of the issues being looked were also examined when Ryanair made its Aer Lingus approach, and when IAG bought BMI - including traffic between Dublin and London and access to Heathrow.
(Additional reporting Reuters)