I have seen several
most did not remain UFO and quickly became IFO. One was a blimp with the sun shining on it at just the right angle. It looked amazingly like a disk but it became obvious after the angle changed in a minute or so.
At least one that my daughter and I saw was never explained but I am confident it was only some visual phenom. While some thing are unidentifiable I have never seen anything that couldn't be explained by something better than an alien craft