Ryanair and Norwegian both saw passenger numbers rise by 11% in May.
The Irish budget carrier flew 11.8 million passengers in the month compared to the same month last year with the load factor up by one percentage point to 95%.
Ryanair’s rolling annual traffic to May grew by 13% to 122.5 million passengers.
Norwegian carried more than 2.9 million passengers in the same month.
Europe’s third largest low-cost carrier took delivery of one Boeing 787-9 Dreamliner and three Boeing 737-800s in May.
Chief executive Bjørn Kjos said: “We are very pleased to see that more passengers chose to fly Norwegian.
“Our international growth continues, in line with the company’s global strategy, enabling us to create more jobs.
“The launch of our new long-haul base in Rome and the routes to New York, Los Angeles and San Francisco have been very well received on both sides of the Atlantic.”
Norwegian operated 99.7% of its scheduled flights in May, of which 82.7% departed on time. The load factor was 86.5%.
EasyJet carryings in May grew by 9.5% to more than 7.5 million passengers with the load factor static at 91.5%