The airline said net profit for the period was 435.9 million Norwegian kroner ($74 million), compared with 628 million kroner a year earlier. It said it spent just over 100 million kroner on replacing the 787s, dubbed Dreamliners, and compensating delayed passengers.
The airline grounded its 787s about a month ago so that Boeing technicians could examine what appears to be a technical problem.
Norwegian spokesman Lasse Sandaker-Nielsen said that the plane "has not been reliable enough and passengers have been subjected to too many delays." He declined to identify the technical glitches encountered.
In the meantime, the Scandinavian low-cost carrier has leased an Airbus A340 to fly on its two new long-haul destinations between Stockholm, Sweden, and New York and Bangkok.
Norwegian Air Shuttle has ordered eight 787s and received two.
Third-quarter sales rose 15 percent to 4.88 billion kroner from 4.22 billion in the same period 2012.
Norwegian has grown rapidly in recent years, expanding international traffic and adding new bases.
Still, the airline said it experienced increased competition in leisure markets and that the warm late summer weather in northern Europe had a negative effect on sales during the quarter.