Are UFO's just bubbles of gas?
Trapped pockets of air between low and high pressure regions create a silvery saucer-shaped phenomenon
This coincides with industrial development that emits various gasses
And explains why these phenomenon became so prevalent around the industrial age
More bubbles form within the main bubble, creating a "spheres turning inside a saucer" shape
I have personally seen 2 while traveling from a high-pressure region to a low-pressure region where atmospheric inversions are common
They are large and look like metal, because the gas in the high pressure bubble reflects light