Singapore Airlines has changed the path of its Seoul-Los Angeles flights after a recent North Korean missile test.
It joins a growing group of airlines who have re-routed planes because of Pyongyang's more frequent launches. They include Lufthansa and Air France, who now avoid the North's airspace.
North Korea does not announce its tests beforehand unlike other countries.
This means their projectiles' flight paths are unknown, posing a possible danger to aeroplanes.
In a statement to the BBC, Singapore Airlines said it made the change after Pyongyang launched an intercontinental ballistic missile (ICBM) in July.
The same missile had also prompted Air France to expand its no-fly zone around North Korea, after the airline found out the projectile may have been as close as 100km (62 miles) to one of its planes .
German carrier Lufthansa told the BBC that it had been avoiding North Korean airspace for more than a year, for services to Japan and South Korea.
It added that since the July missile, it also evaluates "each individual airline route on a daily basis". A decision on whether its planes should avoid the Sea of Japan is also "taken every day".
Recent missiles launched by Pyongyang have landed in Japanese waters.
North Korea's rocket test in September reportedly also led Scandinavian and Swiss Airlines to re-route their flights into Japan.
A Japan Airlines spokesman told the BBC that as of Thursday, all routes were deemed "safe to operate", but they were "prepared to implement any route changes as needed".
On 29 November, Pyongyang fired what it claimed to be a new type of ICBM that could hit mainland US.
Hong Kong airline Cathay Pacific said earlier this week that the crew onboard one of its planes witnessed what they believed to be that missile's re-entry into the atmosphere.