Those are experimental US Aircrafts, like these...What is amazing , the "only superpower of the world" doesn't know what these objects are!!!
Who knows then!!
Alternatively, they most probably know very well what these objects are, but are shying away to tell the world. The cover up continues for last 60 years.
One Change though, at least now, they admit their existence. One day they will admit what these UFO's are , who is flying them.
Sure they are. That's why the US didn't know about them.