Norway's UFO mystery of 1950s finally solved

The CIA has revealed sightings of mysterious flying crafts travelling at high speeds with flashing lights were actually test flights of US military aircraft.

Top secret U2 spy planes flying at 18,000 metres created the phenomena and the CIA recently posted on their Twitter account, reports Aftenposten newspaper, saying: "Do you remember the reports of unusual activity in the sky in the 50's? That was us."

U2s flew at higher altitudes, way above most passenger planes and military aircraft. When the sun set below the horizon the U2s were still high enough to reflect its rays, and other pilots saw them as bright, silvery objects in the night sky, the CIA explained.

The official explanation was kept secret to avoid the Soviets learning of US military intentions during the Cold War .