Ring UFO Appears Over Warwickshire, England, Many Witnesses, April 2014, VIDEO, UFO Sighting News.

Date of sighting: April 2014
Location of sighting:  Warwickshire, England
Source: http://www.mirror.co.uk/news/uk-news/leamington-spa-schoolgirl-takes-picture-3414787

According to the Daily Mirror, 16-year-old Georgina was playing tennis with her mom when she saw the UFO moving past. The pair saw a clearly defined black circle which looked like a giant smoke ring. The UFO hovered for three minutes before it disappeared. Georgina stated that she looked up at the object in the sky and thought "what the hell. It was just floating there like a cloud and then it disappeared. It wasn't birds either. There were about ten of us who stopped what we were doing and watched. It is the weirdest thing I have ever seen." 

The video below of the UFO shows the object over a tree, but end before the UFO disappears, which would have been helpful to see to determine if its a smoke ring or UFO cloaking. SCW

A similar UFO was recorded by some US solders in Sept 1957 at Fort Belvior, Virginia. Private Stone remembered his Kodak Brownie camera which was in his car. He ran over to the car, which was parked nearby, grabbed the camera and took six pictures in fairly rapid sequence. After the second picture was taken, the strange ring started to develop a mist around itself. The mist thickened rapidly until it was more like a small cloud and within 30 to 60 seconds the Black ring was completely enveloped within a small compact cloud of its own.