North Korea allowed foreign airlines to fly through its airspace back in 1997.
A fear remained: the danger of civilian aircraft being shot down.
A real fear: last March, one NRT - SHE China Southern avoided test missiles firings by a few minutes.
Thanks to NorthKoreaTech, we know a bit more. First, here's a map of the region. The author added a line on 132 degrees East latitude—its western side having been declared too dangerous by the FAA.
Looking at FlightRadar24 data reveals one thing: China Southern, nonplussed, keeps flying right through North Korea!
As the codeshare partner, does Japan Airlines even know this?
It's also clear that Lufthansa, Air France, Turkish Airlines, KLM and Finnair are flying westwards of the 132 degrees East latitude.
So maybe look for missile heat signals next time you fly to KIX or NGO from Europe.