The increase was driven by an 80% increase in available seat kilometres over the period with the low cost carrier’s load factor of 88% remaining the same over the two years.
WOW founder and chief executive Skuli Mogensen is confident it will see the growth rate continue this year as the fleet grows to 24 aircraft.
He said: “For WOW air, 2017 was marked by rapid growth and investments throughout our company and fleet.
“We have never been better equipped to continue our future growth and we expect to transfer 3.7 million passengers in the year 2018.
“I look forward to all the exciting developments that are on the horizon, including upcoming new destinations and aircraft, which will ultimately make the WOW journey even more pleasurable for our passengers.”