1- UFOs are rigid, mechanical artifacts.
The current consistent observational data points to the fact that many UFOs are amorphous, shape shifters objects. That was even known to Trevor J. Constable in the 1950's and in the early 1960's that was known to Kenneth Arnold, current observations only confirm and reaffirm what the early pioneers already knew. We already had seen that the insistence in some cases to even mention the "metallic" composition of these objects is really anachronic because then these supposedly mechanic artifacts with very advanced technology will be behind current human technology.
2- There are Hot Spots.
Current observational data from active observers also points to the fact that UFOs/Anomalies can be observed from any location on earth where there are clear skies, there is really not "preferred" location( a Hot Spot), obviously locations with more clear skies will be more convenient to observe UFOs/Anomalies, as astronomers already know for astronomical objects, also it had been noted that many UFOs/Anomalies usually move at high altitudes that implies that from locations already at high altitude more naked eye sightings of UFOs/Anomalies will be reported, Mexico City is one example. But by using infrared spotting and high optical magnification equipment UFOs/Anomalies can be observed from any location with clear skies.
3- UFO activity is higher at night.
This is a HUGE myth reinforced many times by the sightings reports from casual observers, but it is easy to see that any object inside of the atmosphere that is visible at night because it is self-luminous or highly reflective will be visible in daylight, but at night only the portions self-illuminated of this object will be visible, its full structure will be very hard to see even using state of the art night vision equipment. But many UFOs/Anomalies are not self luminous, these will be very hard to spot at night but they will be very easy to observe in daylight, so in reality there are potentially more options to observe UFOs/Anomalies in daylight than at night and the current observational data fully confirms that.
4- UFOs are hard/rare to spot.
This is sometimes not explicitly expressed but assumed, in reality UFOs/Anomalies have an astronomical presence in our planet. If people that are doing regular observations can observe UFOs/Anomalies regularly by just scanning a very small portion of the sky for a very small period of time it will not be very difficult to see that the number of these objects have to be very large in all our planet.
5- Life can only exist on Earth-like planets.
This is not only an Ufology preconception it is also a dominant preconception in Official Science. This preconception/myth assume that Life can only be Carbon based and hence any other place with Life should emulate Earth conditions, but recent developments in the physics of complex plasma strongly suggest that Life can also be based in complex plasma, many UFOs/Anomalies appear to have a plasma-like/electromagnetic composition. If plasma based Life is a reality that Life will be as old as the Universe itself, in comparison Earth itself will be very young, and carbon based life could be a by product of that plasma Life, that plasma Life will be pervasive through all Universe, carbon based Life will be very rare, so in a very concrete sense carbon based lifeforms will be the anomalous/rare lifeforms.
In the same way that if in a relatively small volume self contained complex organic reactions take place for a relatively long period of time this volume will be very likely a carbon based lifeform the physicists of complex plasma had suspected that similarly if in a relatively small volume self contained complex plasma interactions take place for a relatively long period of time then that volume of plasma will be very likely a plasma based lifeform.
6- If intelligent Aliens exists they will be human-like/humanoid.
This is really a very naive myth, just on our planet the body types of living organisms are very diverse, statistically the biped body type is really very small compared to all body types. Furthermore if plasma Life is a reality, and many things point in that direction, an intelligent shape shifter entity will have not defined body type, it will be able to adopt or mimic any shape.
7- There is a coverup hiding the "truth" about UFOs.
Any human community/group will always promote the ideas/facts that reinforce their worldviews, that are agreeable to them and on the other hand they will avoid, belittle, ignore and suppress the ideas/facts that may contradict these worldviews or are not agreeable to them, hence by definition any human group will be doing "coverups" of these not agreeable ideas/facts.
We had seen the reactions of UFO believers to facts or ideas suggesting the reality of amorphous/polymorphic UFOs/Anomalies, similar reactions had been seen from scientists. Can we say that they are coveringup this reality? No really, but they will try very hard to belittle, suppress and ignore it because that reality appears to be in open contradiction to their deep seated worldviews/preconceptions.