International Airline Group carriers all saw improved load factors in June as overall traffic rose by 9.1% year-on-year.
This came as overall capacity for the month grew by 5.4%.
IAG airlines flew 10.6 million passengers last month, up 8.9% on June last year, with North American routes showing the strongest growth of 10.5%.
The total carryings were below the 12.6 million passengers flown by budget rival Ryanair in June.
The load factor at British Airways rose by 3.5 percentage points year-on-year in June to 87.1%, while Aer Lingus saw a rise of 2.2 percentage points to 89.1%.
IAG confirmed last week that its low-cost arm Level would start short-haul operations from Vienna from July 17 with a plan to base four Airbus A321s at the Austrian airport to serve 14 European destinations.