Sadly, many pilots and others are fooled by Venus. Whether you like it or not, that is a fact. For instance, from this link:
It was a terrifying, bizarre event over the Atlantic Ocean, but what makes it even stranger is that, according to a new report from the Transportation Safety Board of Canada, the initial light that first officer saw was an optical illusion. He thought it was a UFO — quite literally, an unidentified object flying at the plane. Yet there was no aircraft, identified or otherwise: he had instead seen reflected sunlight from the planet Venus. (The second set of lights—the ones that caused the evasive action—were actually from another aircraft the pilot mistakenly believed was on a collision course with the Air Canada flight.)
This is just one example of this happening. The first officer took Venus for a UFO, whereas the Captain correctly identified it for what it was. Moreover, from same link:
In fact, Sheaffer noted, "During World War II, B-29 crews making night bombing raids in Japan reported being followed by a 'ball of fire' that turned out to be Venus. Since then, numerous police officers and pilots have made the same mistake, as did Jimmy Carter, who reported seeing a UFO back in 1969 that turned out to be in exactly the same place as Venus."
Emphasis mine. So, if I were you I would be a little careful with such statements and actually go through the literature on the subject matter before brushing off such Earthly explanations. That said, nobody is claiming that Venus is the culprit in every sighting, it is a mishmash of different causes.
Please do list a few cases with physical traces that have not been identified.
No, it is a known fact for those that knows how science works. There is simply nothing whatsoever to work with, hence only the kooks and charlatans are left.
''That's true. There were dozens of soil samples collected by scientists in the 50's and 60's. They all had natural explanations. Case closed.''
Which mean either you were overlooking on purpose the physical traces cases (which most have nothing to do with abductions or invitations in a craft) and took place the following decades or you simply were not aware of them.
Again, please list a few of the unexplained physical trace cases.
To quote a catalogue article by Ted Phillips:
This summary is based on only a partial listing of the catalogue as many of Phillips' cases appear extremely dubious in nature. Cases from the early 1950s are particularly unreliable because many of the early UFO books were written by people who automatically assumed that they were describing encounters with alien spaceships. Jenny Randles tells me that cases reported in the "hysterical" Spanish and South American media should be treated even more skeptically because these cases were often complete fabrications! Furthermore many of the early cases have no proper source, e.g. Phillips quotes Vallee describing cases which appear to have been anecdotally reported to Vallee. This means that we often have no idea whether or not a specific case was investigated by anyone, let alone whether it was a contemporary investigation or whether the investigator was in any sense someone capable of undertaking an objective scientific evaluation.
Precisely, this has to be done under controlled conditions, which is simply impossible. And whether you like it or not, witness testimony carry no weight whatsoever in scientific circles, only hard data matters. I can claim I have an experiment that have photons travel faster than light, but unless I have hard data to show for my claims, I have nothing. Same with UFOlogy, if science is to get involved, we need hard data obtained under controller conditions, which is an impossibility as it currently stands. If you disagree, I would very much like to hear how you suggest that be done.