As the typology / anatomy of extraterrestrial beings, the ships follow the same pattern of recognition. Not all images are safe for the physical evidence required by many scholars that are based on reported sightings of flying objects.
The formats are too varied, the standard models would be more sightings in 2004, the traditional and more popularly known, Discoid, shape Spherical, Cylindrical and Triangular.
If we put more detail you can reach a number around 35 different models of UFOs. These include ovoid and conical shapes. These formats would be in accordance with the ideals for space engineers crossings in space, but our technology today was not suitable for launching a space in this aircraft geometry, the most that have been made satellites, at least that was released to the free press.
The issue of variation of UFOs also clashes with the culture of the individual who saw along the human history we find many reports of UFOs, then describes each of these ships as they could understand, Flaming is like chariots, winged horses, fiery clouds, gods, and others, very common to be found in ancient texts. Even today, this variation occurs in the interpretation of the object viewed, but in all there are similarities.
A detail raised by some ufologists is that the wave of sightings of UFOs have higher numbers and some sync with some events of our society as the Industrial Revolution, First and Second World Wars, or in tests of military weapons . These high incidents of reported sightings are always more in times that the planet goes through some kind danger by ignorance or lack of accountability of governments about the domino effect that some attitudes or tests bring. An example is the famous case of the Chernobyl Nuclear Power Plant in Ukraine in 1986, of radioactivity after the accident, many people spotted UFOs on the region, with some of these reportedly remained on top of a reactor that had not exploded. Fun facts to be reflected.
But back to the types of existing Naves, besides the main 04 can cite some as
Adamskiano: this is named after one of his contacted Polish George Adamski, who reports that the three lower spheres serve to propel the craft.
Bell: this is one of the least seen worldwide, with most reported in Australia from New Guinea.
Cigar: ship long, usually cylindrical in its tip flattens. Very reported as mother ship, by leaving small UFOs from inside.
Beehive: spherical shape with details like windows, usually leaves a trail of white smoke into the air or light.
Although they have different names end up being variations of 04 main types, because of this classification was dried for better identification of cases. The following images show the illustration (outline) of some of these UFOs seen around the world. Of course, these studies become somewhat superficial, since the workings of these technologies are not yet understood by us, leaving only the engineers expect to prepare studies or open our minds to new information given by these visitors for such a long time.