Airlines around the world have abandoned routes passing through North Korea's flight information region (FIR), the shortest distance from the U.S. to South Korea, due to the North's constant missile launches.
Flight times have increased by 30 to 40 minutes, requiring more fuel and costing carriers billions.
North Korea informed the International Civil Aviation Organization of impending missile launches until February last year but then stopped.
According to the Ministry of Land, Infrastructure and Transport on Tuesday, 34 airlines from 17 countries used Pyongyang's FIR when flying to South Korea in 2015, but as of last month only seven Russian carriers are still using it. The number had already fallen to 25 last year.
ICAO has divided skies around the world into FIRs allocated to different countries and entrusted them with providing safety information to overflying aircraft.
South Korean airlines stopped using Pyongyang's FIR in 2010, when Seoul began implementing sanctions against North Korea. Instead, planes from the U.S. fly over Japan, which takes 30 to 40 minutes longer to get to Incheon.
ICAO has designated two "danger areas" on maps that are potential zones where North Korean missiles may fall and told airlines to avoid them. The U.S. Federal Aviation Administration banned American carriers from using Pyongyang's FIR last month.
Singapore Airlines in July changed flight routes connecting Incheon and Los Angeles and is using a route further south that passes over Busan and the east coast of Japan rather than Gangwon Province and the East Sea, into which North Korea often lobs its missiles.
The chances of a civilian aircraft being hit by a North Korean missile are extremely low, but safety must come first. No accidents have occurred so far, but the pilots of several commercial flights have seen North Korean missiles whizz through the sky.