It hadn't previously announced the changes before this week.
While Singapore Airlines have continued to avoid the area, a flight crew on a different airline last Wednesday reported seeing North Korea's latest ICBM launch.
While ICAO has urged airlines to take precautions, the agency is not advocating for a no-fly zone, because such a move would be disruptive for carriers and it's not clear where North Korea will fire missiles during tests.
"There are no current routes that fly through a risky zone", said an Asiana Airlines official. "We remain alert and [will] review the situation as it evolves".
The closest shave was on Nov 29, where crew on at least three commercial flights from Korean Air and Cathay Pacific reportedly saw the North Korean missile in the air before it blew up near their location.
Korean carrier Asiana Airlines also changed flight paths on some of its routes between Korea and the U.S. in 2010 in order to avoid the risk of being hit by an unexpected missile. The flights, one from San Francisco and the other from Los Angeles, were both headed for Incheon, the main airport serving Seoul, South Korea. The most recent incident was when the crew of Cathay Pacific and Korean Air spotted the Hwasong 15 missile launched last week by North Korea.
The test-launch raised tension further with South Korea and the United States, who on Monday began their largest ever joint air exercise, which the North has branded an "all-out provocation". The chances are "billions to one", aviation safety analyst David Soucie told CNN. North Korea likely chooses splashdown points for each stage that avoid airline routes, said Vipin Narang, an expert on nuclear strategy at the Massachusetts Institute of Technology.
Katherine Lam is a breaking and trending news digital producer for Fox News.