IAG has offered to connect passengers from Ireland with rivals' long-haul flights out of London in an attempt to allay European Union competition concerns over its bid for Aer Lingus.
This is according to the Bloomberg news agency, who cited two people with knowledge of the matter.
Bloomberg said the concession is designed in particular to assuage Richard Branson's Virgin Atlantic Airways, which has expressed competition concerns about the deal, according to the people.
IAG has not made any offer to surrender London Heathrow slots of the combined group, the sources said.
Buying Aer Lingus would win IAG scarce take-off and landing positions at Heathrow, Europe's top hub, where British Airways is the biggest carrier, as well as opening up trans-Atlantic routes via Ireland.
IAG agreed to buy Deutsche Lufthansa's BMI unit in 2011 to gain slots.
The European Commission said yesterday that International Consolidated Airlines Group had offered competition remedies to help win approval for its planned €1.35 billion deal.
The EU's competition regulator extended its preliminary deadline to review the accord to July 15.
The concession would build on IAG's pledge in 2012 to feed competitors' long-haul flights from Heathrow as it secured the EU's backing for its takeover of BMI.
IAG said its engagement with the Brussels-based Commission is ongoing and declined to comment further, Bloomberg said.
Virgin Atlantic said its position has not changed and that guarantees need to be made to ensure IAG works with Aer Lingus' existing partners. The Commission declined to comment.
The EU will seek industry feedback on the IAG's concessions, one of the people said.
IAG made its first indicative offer for Aer Lingus in December. It took the company a further five months to get the
Government's backing, amid negotiations over jobs, the future of Aer Lingus's Heathrow slots and routes from Ireland to London.
EU officials raised no major objections in May on state-aid grounds to IAG's pledge to maintain Ireland-to-London routes for seven years to win the state's 25% Aer Lingus stake, people with knowledge of the informal discussions said at the time.
Ryanair, which owns almost 30% of Aer Lingus, has not said whether it supports the IAG deal. Earlier this month, the UK's Competition and Markets Authority said that it still required Ryanair to cut its Aer Lingus stake to no more than 5%.