What happened
On November 17, 1986, at around 5:10 p.m. local time, a Japan Air Lines Boeing 747 freighter was flying from Iceland to Anchorage. Over eastern Alaska, Captain Kenju Terauchi and his crew saw two sets of lights that flew alongside the plane for several minutes, illuminating the cockpit. Later, against the lights of a town, Terauchi made out the outline of a huge walnut-shaped object, many times larger than the aircraft. Controllers in Anchorage approved course changes, and indistinct returns appeared on civilian and military radar. The encounter lasted about 50 minutes. The FAA investigated the case, and in January 1987 it made headlines around the world.
Witnesses
Captain Kenju Terauchi, copilot Takanori Tamefuji, and flight engineer Yoshio Tsukuda; air traffic controllers in Anchorage.
Explanations and hypotheses
The FAA concluded that the radar returns were most likely clutter and did not confirm the presence of a second object. Philip Klass argued that the lights may have been Jupiter and Mars low over the horizon and the huge object an illusion. The other crew members did not see the large shape. Critics of this explanation point to the correlation between the sighting and the radar data. Years later, former FAA division chief John Callahan claimed that the CIA had taken the data.
Disputed A likely explanation exists, but some of the facts are still disputed.
More: Wikipedia (en)