Alleged UFO encounter
Japan Air Lines Cargo Flight 1628 was a Japanese Boeing 747-200F cargo aircraft flying from Paris to Narita International Airport that was involved in an unidentified flying object (UFO) sighting on November 17, 1986. During the flight, Captain Kenji Terauchi reported seeing three objects he described as "two small ships and the mothership". The FAA in Anchorage only saw Flight 1628 on their radar. Two other nearby planes only saw Flight 1628 and no other objects. An FAA investigation of the incident characterized Terauchi as a "UFO repeater". Astronomers and investigators have determined that Terauchi probably mistook the planets Jupiter and Mars as UFOs. Contradictions among the accounts of the crew from the three aircraft as well as contradictions between the transcripts and later interviews with Terauchi have cast doubt that anything unusual happened.
Observation.
On the Reykjavík to Anchorage section of the flight, flying at , at 17:11 over eastern Alaska, the pilot, Captain Kenji Terauchi reported seeing three unidentified objects, "flying parallel and then ... very close". News media of the time reported that Terauchi referred to the objects as "the two small ships and the mother ship", and as "two small ones and one twice the size of an aircraft carrier". After six minutes, Terauchi radioed the Anchorage Federal Aviation Administration who advised him to take "evasive action". Terauchi decreased altitude and turned the plane in a circle, but reported that the lights were still with the plane after the turns.
At the time, news media stated that the FAA reported seeing objects near the plane even after the evasive maneuvers, but upon later review, the military radar images were "dismissed as clutter, and an object that showed up on the aviation agency's screens was thought to be a coincidental split image of the aircraft". Fairbanks FAA air controllers saw only Flight 1628 on their radar screens.
Terauchi reported that the objects followed the plane for . Two planes that were near Flight 1628, a United Airlines and an Air Force C-130 cargo plane reported that they did not see any objects either visually or on radar. 
Flight 1628 landed in Anchorage, the crew were debriefed and FAA investigators determined "they were 'normal, professional, rational, (and had) no drug or alcohol involvement'".
Explanation.
Editor of "Aviation Week and Space Technology" magazine and UFO investigator Phillip J. Klass reported that the planets Jupiter and Mars were in the area that Teruchi said he saw two lights, and although they would have been quite visible, he did not mention seeing them. Klass states that it is not unusual for an experienced pilot to "mistake[n] a bright celestial body for a UFO, nor will it be the last. ... Jupiter was only 10 degrees above the horizon, making it appear to the pilot to be roughly at his own 35,000-foot altitude". Klass noted that when the crew was interviewed separately in 1988, their remembrance of the event differed significantly.
According to Klass, the pilot later contradicted what he told flight controllers at the time of the incident. After reviewing transcripts of the radio communications, an FAA spokesperson stated that the pilot told the ground controllers that he lost "sight of the object after completing his turn". But in a later interview, the spokesperson said that Terauchi said the "object stayed with him as he turned". 
The FAA released a data package of the incident characterizing Terauchi as a "'UFO repeater', having reported two other UFO sightings prior to November 17th, and two more this past January". In a January 11, 1987 UFO sighting reported by Terauchi in the same general area as Flight 1628, he stated he saw "irregular pulsating lights ... [and] a large black chunk just in front of us". The FAA radar did not confirm an object, and the event was later determined to have been "lights from small villages being diffused by thin clouds of ice crystals". Klass notes that Terauchi used the words "spaceship or mothership" in his reports and claimed that the "mothership ... did not want to be seen". Teruchi also claimed that "we humans will meet them in the near future".
According to astronomer and UFO investigator Robert Sheaffer, despite Flight 1628 becoming one of "the most celebrated cases in recent UFO literature, it turns out there wasn't much to read". About Terauchi's report, Sheaffer states that the pilot is not "an unbiased or objective observer". Science writer Brian Dunning writes that there was "nothing extraordinary or unusual on that evening" calling Terauchi "a fine and competent pilot, but was hardly unbiased when it came to alien spaceships" and Flight 1628 "just another unevidenced aerial anecdote".
References.
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