They may not be out of this world, but these ‘UFO clouds’ certainly made onlookers in Aberdeen wonder.
However, weather experts said any thoughts that the sky signalled an impending alien invasion were pie in the sky.
Lenticular clouds, as they are called, are formed when stable moist air flows over a range of mountains.
A series of large-scale waves can form on the downwind side and if the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds.
Claire Stewart, 37, of Kincorth, Aberdeen, made the sighting while looking out over her back garden in Kincorth, Aberdeen on Monday morning.
She said: “I was just looking out from my home in Kincorth when I saw the cloud.
“It looked like a UFO and I had to double take before I realised it was actually a cloud.
“I’ve never seen anything like it before, but apparently they’re called lenticular clouds.
“It’s very weird.”
The clouds have been mistaken for UFOs in the past because of their smooth saucer-like shape.
A Met Office spokeswoman said the cloud was likely to have been formed over the Cairngorms.
She said: “These photos show an excellent example of a cloud called Altocumuls Lenticularis.
“Lenticular clouds can form at heights between 6,500 and 16,500 ft, and are called lenticular because of their lens shape
“The clouds can be seen as far as 60 miles downwind of the hills or mountains that led to their formation and they are believed to be one of the most common explanations for UFO sightings across the world.”