Operating profit rose to €960mln in the three months to June 30 from €816mln last year, beating analysts’ forecasts of €914mln.
Total revenue increased to €6.7bn from €6.2bn last year. Passenger unit revenue for the quarter grew 3.1% or 1.1% at constant currency, boosted by the later timing of Easter this year.
Passenger numbers rose to 55.9mln from 52.7mln last year. The load factor – the number of passengers against the number of seats available – grew 0.6 points to 83.0%.
Fuel unit costs gained 12.4% or 6.3% at constant currency.
"Despite fuel cost headwinds, we delivered a good performance,” said chief executive Willie Walsh.
The interim results come two days after British Airways lost an appeal aimed at stopping a planned strike by pilots.
The British Airline Pilots' Association (Balpa) backed industrial action on 22 July after three days of negotiations failed to resolve the dispute.
IAG launched an appeal after it lost an injunction to halt the strike in the High Court. The Court of Appeal rejected the appeal on Wednesday.
Shares advanced 3.6% to 428p in morning trading.