Alien conspiracy theorists claim some alleged flying saucers are equipped with a substance that can male a cloud around them say they can hover above us seemingly unnoticed.
The claim usually does the rounds on online conspiracy theory forums after photographs of lenticular clouds – such as these snapped above mountains on Are, Sweden, are uploaded to the internet.
Photographer Sara Björkebaum joked on Instagram: “I thought I could jump on that spaceship,” after posting the pictures on her page.”
The cloud appeared in the mountains of the ski resort of Are, in Sweden , causing people to stare in wonder and bewilderment.
But, while Sara knew it was just an odd-shaped cloud, there are many alien chaser who believe there is actually a UFO inside them when they appear.
The alleged disguise is known as a cloaking device to conspiracy theorists such as Scott C Waring, who runs website ufosightingsdaily.com.
He blogged about another lenticular cloud image taken over California: “UFOs make clouds, that’s just a fact. We have reported hundreds of UFOs hiding in or near clouds over the years.
“Here we have a giant UFO shaped cloud. The shape is disk like because the UFO is disk shaped, but much smaller…about 10 per cent the size of the cloud.
“The layers are made because the disk decides to rise up or lower, but its making the cloud at the same time, so it appears a new layer is there.”
But, the truth is lenticular clouds are a phenomenon that happen only with precise meteorological conditions
They are caused by so-called orographic waves, which are static waves formed in the atmosphere.
They happen when a current of air hits a mountainous relief, deflecting the flow upwards. Lenticular clouds, usually give the illusion of being motionless in the sky until they disappear.
And, not all readers of ufosightingsdaily.com are impressed by Mr Waring’s theory.
A user called Jaz Man posted on the site: “To claim that this is a UFO is just ridiculous.
“Lenticular clouds are stationary lens-shaped clouds that form in the troposphere, normally in perpendicular alignment to the wind direction.”