The change involves the airline's Seoul-Los Angeles flights and was put in place following Pyongyang's July 27 missile launch into the Sea of Japan, the company reportedly told Channel NewsAsia.
North Korea has received global criticism for its missile launches. The International Civil Aviation Organization (ICAO) in October condemned the rogue state for its repeated launches, saying they severely undermined the safety of international civilian flying.
North Korea, a member of the ICAO, is required to provide prior notice of any activity that could threaten civil aviation, the report said.
News of Singapore Airlines' change followed a crew on board a Cathay Pacific aircraft seeing a North Korean missile blow up over the Sea of Japan last week.
Pyongyang launched the latest in a series of ballistic missiles last Wednesday in defiance of international sanctions and warnings against provocations. The rocket, which the regime said could reach the U.S. mainland, crashed into the sea near Japan.
The crew of Cathay Pacific CX893, which was traveling to Hong Kong from San Francisco, reportedly saw the missile from their plane as it was passing over Japan and alerted the country's air traffic control.
—CNBC's Holly Ellyatt contributed to this report.