Its yield, or revenue per passenger carried and km flown, rose to 0.46 Norwegian crowns ($0.0514) in August from 0.45 crowns a year earlier, in line with forecasts in a Reuters poll.

Europe's third largest budget carrier on Monday asked bondholders for up to two more years to pay back $380 million of outstanding debt in the loss-making airline's latest attempt to shore up its finances.

Norwegian switched this year to prioritise profits over growth, but that goal is being hampered by the global grounding of Boeing's 737 MAX aircraft and long-running technical problems with Rolls Royce engines on Boeing Dreamliners.

The company's capacity expansion, as measured by available seat km (ASK), peaked at 51% growth year on year in June 2018 and has since declined.

It expanded by 4% in August while analysts in the Reuters poll had forecast a 2.6% increase.

"Our growth is slowing down, in line with our strategy, and we are glad to see an increased unit revenue this month compared to the same month last year," acting chief executive Geir Karlsen said in a statement.

"We are also pleased that bookings are looking solid going forward, especially on intercontinental routes and in the Nordics," he said.