Low-cost carrier Norwegian saw May carryings rise by 13% to almost 2.4 million passengers.
However, the month’s traffic figures compare to weak numbers in May last year when the airline was affected by a strike by cabin crew.
Norwegian reported that passengers have returned, even after the pilot strike earlier this year which affected future bookings.
The load factor for last month was 84.9%, up 7.9 percentage points year-on-year.
Chief executive, Bjørn Kjos, said: “I´m very pleased with the solid traffic figures, even though the growth seems even stronger in light of the weak May last year.
“Still, the traffic figures show that an increasing number of customers choose Norwegian.
“Future summer booking figures are positive, which not least reflect our European and intercontinental growth.”
EasyJet achieved a 7.2% rise in carryings last month to 6.4 million passengers over May 2014.
The load factor rose by 2.2 percentage points to 91.6%.
The budget carrier’s annual passenger numbers rose by 6.1 to 66.6 million in the year to May.
Passengers carried by Wizz Air rose by 20% to 1.8 million in May over the same month in 2014 with an improved load factor of 89%