British Airways owner IAG SA’s Irish and Spanish businesses spurred gains in passenger traffic at the company last year as expansion at the U.K. arm slowed. Dublin-based Aer Lingus, purchased by IAG in 2015, posted a 12 percent traffic increase, while the advance at Madrid-based Iberia accelerated to 7.6 percent, according to a statement from the group Thursday. London-based IAG, as International Consolidated Airlines Group SA is known, has been pouring resources into a turnaround of Iberia and Aer Lingus, historically two of Europe’s worst-performing carriers. BA’s traffic growth slipped to 1.5 percent as it almost froze capacity to combat a glut in seats and bolster fares. The unit’s earnings have begun to recover from the Brexit vote in 2016, which triggered a collapse in the pound, reducing the value of sales converted into euros, IAG’s reporting currency. Expansion also slowed at Barcelona-based discount carrier Vueling, which reported a 3.8 percent increase in traffic, a measure of passengers carried times the distance flown that’s a standard performance indicator for airlines. IAG’s overall traffic also rose 3.8 percent, slowing from a 4.5 percent gain in 2016, while the passenger tally increased 4.1 percent to almost 105 million. The company didn’t break out figures for its Level unit, a low-cost, long-haul operation that has begun flying from Barcelona and plans to add services from Paris this year. The unit’s traffic is currently included with Iberia’s numbers.