Air Berlin, Germany's second-biggest airline after Lufthansa, said the number of passengers its planes carried in May rose by 1.8 percent year-on-year.

Passenger volume rose to 2.9 million in the month, Air Berlin said on June 7.

But its load factor -- a measure of capacity utilisation -- narrowed to 74.0 percent from 76.7 percent a year earlier.

Fare yield dropped 6.9 percent to 5.48 cents because customers were reluctant to book after ash spread from an erupting volcano in Iceland had disrupted air travel.

Airlines are reeling from the aviation industry's worst year ever, in which demand dropped faster than capacity could be cut. Air Berlin started adding more seats again in November.