A MYSTERIOUS black line across the sky above Horwich has left one resident scratching his head.

The strange black line appeared in the sky in Bolton on Tuesday afternoon and was snapped by Bolton resident Sean Corless, who was convinced the line was a tornado.

Mr Corless, aged 46, of Regent Road, Lostock, said: "I was visiting an elderly family member in a nursing home in Horwich and I looked up and this black line was really significant in the sky.

"I was convinced I was seeing a twister or a tornado or something — it looked like a whirlwind, but this line arched right up and across the sky.

"It spooked me out."

After looking on the internet Mr Corless thinks the line may be a vapour trail from a plane, caused when hot humid air from jet exhaust mixes with environmental air of low vapour pressure and low temperature.

Mr Corless added: "There are a lot of conspiracy theories on the internet as to what it could have been, some have even said it's aliens, but when I saw it I just thought I had to get a snap of it because of how unusual it looked."

What do you think it is? Post your suggestions below.