Aer Lingus led IAG's passenger traffic gains last year, as expansion at British Airways (BA) slowed. IAG bought Aer Lingus in 2015.
The Irish airline posted a 12pc traffic increase last year, while Madrid-based Iberia's numbers were up 7.6pc, IAG said yesterday. BA's traffic growth was 1.5pc.
Numbers for Level, IAG's new low-cost brand, were included in Iberia's total.
Willie Walsh's IAG has poured resources into a turnaround of Iberia and boosted Aer Lingus with new planes.
IAG's overall traffic rose 3.8pc, slowing from a 4.5pc gain in 2016.
Its passenger tally increased 4.1pc to almost 105 million.