An Air France plane carrying more than 330 passengers may have come as close as 100km (62 miles) to a intercontinental ballistic missile launched by North Korea, officials say.
The flight passed the spot where the missile landed about 10 minutes later.
Air France says its plane was not in danger but that it is extending its no-fly zone around North Korea as a precaution.
The Pentagon says the missile flew through busy airspace.
US officials have frequently warned of the dangers posed by missiles to commercial aircraft in the area.
The flight path of the Boeing 777 shows that it was west of Hokkaido, the northernmost of Japan's main islands, as the North Korean missile was in the air.
Japanese and US estimates say the missile came down as close as 100km to 150km to the airliner.
"It flew into space. It landed in Japan's exclusive economic zone, an area that's used by commercial and fishing vessels," Pentagon spokesman Capt Jeff Davis said.
"All of this completely uncoordinated."
Air France has insisted that the missile did not interfere in any way with its flight path and that Friday's service went ahead without any problems.
"The information available to Air France at this stage indicates that the missile was damaged at sea more than 100km from the trajectory of its aircraft," airline officials told RFI (in French). However, even if this distance was proven, it would not question the safety of the flight, the firm said.
The airline added that it continuously assessed possible risks and often adjusted flight plans as a precaution, which was why the no-flight zone around North Korea has been expanded.
In July 2014, Malaysia Airlines flight MH17, going from Amsterdam to Kuala Lumpur, crashed after being allegedly hit by a Russian-made Buk missile over eastern Ukraine. A total of 283 passengers were killed.