Lights in Norway's sky were spy planes

U2 plane Image copyright Getty Images

Norway in the 1950s was gripped by sensational reports of UFOs, with pilots seeing mysterious craft hurtling ahead of them at incredible speeds.

These reports were matched by people on the ground who said they had seen flashing objects implausibly high in the sky.

Now the mystery is over, Aftenposten newspaper reports. What Norwegians were seeing were test flights of top secret U2 spy planes, according to a recent tweet from the CIA's Twitter account, which says: "Do you remember the reports of unusual activity in the sky in the 50's? That was us."

U2s flew at altitudes above 60,000ft (18,000m) at a time when most passenger planes cruised at 10-20,000ft, and military aircraft rarely exceeded 40,000ft. 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 said.

The US Air Force's Project Blue Book investigation into unexplained aerial phenomena concluded that Norwegian sightings tallied with U2 flights. The information was kept classified to shield the spy programme from the Soviets at the height of the Cold War, Aftenposten says.

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