Table of UFO shapes by Paul Hill NASA aeronautical engineer.

Table of UFO shapes, from the classic book "Unconventional Flying Objects" by Paul Hill (a NASA aeronautical engineer who developed an interest in UFOs in the 1950s -after having two sightings of his own- and privately studied UFOs for years). His list of UFO shapes above, does not include the very large V-shaped (boomerang / crescent), the triangular and the smaller triangular/pyramid UFOs.

Those were quite rare in the 1950s - 1970s, when Paul Hill collected data and wrote his book, but became very common in the 1980s and beyond (there are several documented sightings of very large black triangular UFOs even in the 1960s, so it's not a contemporary phenomenon). [Request: If you're an experienced user of computer graphics/drawing software, consider re-drawing this table of UFO shapes above and send me a copy to put here, TIA. Note that the "saturn" shape is not a perfect sphere, but a "flattened" one - see the photo of the Trindade UFO inside.]

Reference : www.hyper.net/ufo/summary.html.