Ellsworth UFO sighting The Ellsworth UFO case occurred in 1953 . Important Radar - Visual UFO . On August 5 and August 6 , 1953 the US Military investigated a UFO incident in Bismarck , North Dakota . What has become known as the Ellsworth Case is one of the most significant radar - visual cases in the annals of UFO sightings . The event was witnessed by almost forty - five agitated citizens along with military Air Defense System personnel . The object was first sighted by Miss Kellian at 8 : 00 P . M . on August 5 . The description was of a red glowing light making long sweeping movements . Erratic Motion Observed . The information was transmitted to the Bismarck , North Dakota , Air Defense Filter Center . Sometime later Sergeant Harry spotted the objects from the roof . He observed , paying close attention to the irregular movement , as it danced between telephone lines . Others on duty saw the moving light which would be visible in the night sky for approximately three hours . Sergeant Harry described his observance in the following manner : " It would remain stationary - - then hop up several degrees very quickly - - almost simultaneously . " Another witness commented , " It would stop . . . move to the left and then swerve down in a sort of slanting motion , repeating these maneuvers several times . " Immense Luminosity Seen By F - 84 Pilots . At midnight three additional objects appeared in the sky above Dakota . The employees of the Filter Center had a feeling like someone was watching them . Before they were seen in Bismarck , two F - 84 s had been vectored into the area over Blackhawk , South Dakota . The objects and the jets were monitored on radar . One pilot established visual contact for twenty to thirty seconds . His description could be heard over the intercom . " It ' s brighter than the brightest star I ' ve ever seen . " When the pilot gave chase the light inexplicably disappeared . Lieutenant Needham , the second pilot spotted one of the objects at 15 , 000 feet . It was below him and to his right . The object moved spasmodically up and down . The colors changed from white to green . In pursuit Needham climbed to 26 , 000 feet . He changed course to 360 degrees . After maintaining steady on 360 degrees for a brief time , his radar lock - on - light on the A - 4 gun - sight came on and remained on . The object was ahead of him . It increased speed and moved rapidly ahead and up . The chase was being carried on the radarscope at the control room . Radar indicated that the UFO was staying five to ten miles ahead of the Lieutenant and his F - 84 . Finally Lieutenant Needham gave up his pursuit and flew back to the Military base . The object continued on and was detected by the Filter Center in Bismarck . Varied Colors Emulate A Wave . At 1 : 09 A . M . an Air Force Globemaster Globemaster II flew over Bismarck . As the plane neared , the object closest to the plane appeared to emanate a signal by blinking red and green . This signaling was picked up by the other three objects . An observer reflected about this , " It was as if a ' wave ' passed from one to the other . " A signaling effect influenced a then - classified Air Force report filed by Dr . Hynek . He concluded , " The entire incident , in my opinion , has too much of an Alice in Wonderland flavor for comfort . " In the late 1970s Hynek confirmed his conclusion , " That ' s exactly how I felt at the time . " The Air Force offered a number of possibilities as to the cause of the sightings . In the final synopsis the objects would continue on the records as " unknowns " .