International Airlines Group (IAG), the parent company of British Airways and Iberia, posted an 8.9% increase in passenger traffic in June compared with the same month in 2011.
Capacity grew 5.8% and load factor increased by 2.3 percentage points to 84%.
Group premium traffic for June grew by 5.3% year-on-year, compared to 9.6% growth in non-premium traffic.
British Airways recorded an 11.3% increase in passenger traffic during the month alongside a 7.1% growth in capacity. Freight traffic grew 4.5%.
Iberia posted a 3.2% increase in passenger traffic and a 2.7% increase in capacity, with freight traffic falling by 14.3%.
Iberia notes that on 22 June it appealed an arbitrator's decision in relation to an industrual dispute with pilots' union Sepla.
"The appeal relates to concerns that, among other reasons, the arbitrator went beyond his mandate and made a decision that will adversely affect management's ability to maintain an appropriate cost base for the business," the airline says, without giving further details.