The company is planning to buy the airline and has agreed a deal with the Irish government for its stake.
IAG chief executive Willie Walsh said: "We will continue to serve (the Northern Ireland) market."
The first and deputy first ministers had called for the full retention of services between Belfast and Heathrow run by Aer Lingus and British Airways.
The two airlines, owned by IAG, operate 63 services between them each week from George Belfast Belfast City Airport to and from London.
Mr Walsh said: "We will continue to serve that market because it is a good market.
"I see opportunities to work with the airport to see if we can enhance that.
"It is definitely a market we will continue to serve."
Mr Walsh's comments, while not directly pledging to continue both services at present levels, will be seen as providing some initial assurance.
There would be concern if the George Belfast Belfast City Airport were to lose any of its Heathrow flights, used by almost 700,000 passengers each year.
After the Irish government agreed to sell its 25% stake, attention now switches to Ryanair.
It owns 30% of Aer Lingus and Mr Walsh said an offer would be made for its shares within the next 28 days.
If agreement is reached, it would result in a 1.4bn euro (Â£1bn) takeover of Ireland's national carrier by IAG.
Belfast could benefit from a takeover of Aer Lingus, International Airlines Group (IAG) has said.