A baffled British couple has revealed eerie photos of what they claim is a UFO flying over the Cape Verde coast.
The couple, who do not wish to be named, claim they spotted the metallic blue shape when looking back over holiday snaps the next day and had no idea it was there at the time.
“It's just so very strange,” the man said.
"I remember on the day it was so beautiful and we were taking pictures of the scenery.
"I was just looking back through my photos after the holiday and I looked at this one, pointed at the object in the centre, and said 'what on earth is that?’.
"I suppose it looks like a black dot in the background. We just couldn't figure out what it was exactly."
The woman says she had no idea the 'UFO' was in the sky at the time because when she was there she was too busy looking out into the sea, and there were no obvious signs of overhead aircraft.
"What's strange is that I didn't see it at the time because it looked like there were no planes in the sky," she says.
"It was a clear day and it must have been very quick because I didn't notice anything flying in the air at the time.
In a bid to get answers on and identify the mystery object, she has employed the help of a UFO specialist in an effort to get to the truth.
"Some people have suggested that it might be a fly or a drone but I just don't know what it is,” she says.
"I'd just like to speak to some people to get some answers. There weren't any planes in the sky or any helicopters so. It's just so unusual.
"Nobody has been able to tell me what it was. I'm really keen to get it out there to see what people's views are.”
The unidentified object, spotted while the pair were sightseeing on the island of Sal, has a similar shape to a Lockheed SR-71 Jet. The Lockheed 'Blackbird' was a Cold War-era jet but was retired in the 1990s.
Many conspiracy theorists believe the supersonic knowhow that the 'world's fastest jet' used came from alien technology hidden by the US government.
UFO expert Philip Mantle acknowledges it bears an uncanny resemblance to the Blackbird but says the image remains open to speculation.
"Even though it looks like a 'Blackbird Jet' those aircraft were taken out of service long ago and replaced by more up to date stealth technology,” Philip says.
"But it could have been somebody playing on the beach with a drone or it could have been a tourist aircraft of some kind.
"If I'm honest it looks like either a bug of some sort or simply a piece of air borne debris.
“My experience down the years has taught me that people put forward such photos and say that they observed nothing unusual at the time.
"Then it almost always turns out to have a perfectly rational explanation.”
With additional reporting by Caters News.