Soviet air defence radar spotted the plane approximately 400 kilometres (250 mi) away from Soviet territorial waters.[5] At first, the Soviets assumed the plane was a naval aircraft that was returning from a mission, having forgotten to change its IFF transponder code. When the Korean aircraft passed over the Kola Peninsula at 21:19 (Moscow time), Soviet air defence dispatched Alexander Bosov to intercept.[citation needed]
Flight 902 departed from Paris, France on a course to Seoul, South Korea. The plane’s only scheduled stop was in Anchorage, Alaska, USA where it would refuel and proceed to Seoul, avoiding Soviet airspace. As the plane passed over Alert[4] on Ellesmere Island — located about 800 km (500 miles) from the North Pole — flight captain Kim Chang Ky (alternatively spelled Kyi or Kyu) suddenly changed his course and headed southeast toward Murmansk.
The aircraft was not fitted with an inertial navigation system, and GPS navigation was not available at the time. Due to an error in calculating magnetic declination, the plane flew in an enormous, right-turning arc. (The location of the turn corresponded quite closely with the location of the North Magnetic Pole, which is likely to have contributed to, if not directly caused, the error.) It flew southeast over the Svalbard archipelago and the Barents Sea, past northern Scandinavia and into Soviet airspace.