As it turns out, there is a fairly simple explanation for these cloud-like flying saucers.
Clouds. Some really weird clouds.
The odd formations are really “lenticular clouds,” created when warm humid air is thrust rapidly upward into cooler regions, the meteorologists said. It usually happens when warm air is forced up and over mountains but can also occur in the absence of mountains. (mySA)
Mistaking these clouds for UFOs might appear to be an amateur mistake, but it is actually a fairly common one. In 2009, this video made waves when it portrayed this very bizarre object floating in the air above Moscow. Many eyewitnesses said it absolutely did not appear natural.
These clouds can be super tricky, but they are truly just clouds. Since they commonly form in mountainous areas, when they form elsewhere, they tend to be unknown to people and so folks are more prone to their trickery. A good rule of thumb: If you ever see a UFO that could be a cloud, chances are good that it probably is one.
