We have had visitors from other planets for many years
From the times before Old Testament to today, we have had visitors looking after us. Back in the old days no effort was made to hide their ships. Inside of caves occupied by prehistoric man we see cave paintings that certainly look like the classic flying saucer. In order to draw these objects they must have seen them.
In the old testament we see references to fiery chariots in the sky. The people who wrote the old testament had no reference point for air ships of any kind and had to describe them in the context of what they knew. In Ezekiel the description was of a wheel within a wheel again the description had to fit what knowledge they had at that time.
In renaissance artwork we see images of the classic flying saucer, often including a person looking toward it. In my mind the evidence is overwhelming that mankind has been seeing something since the beginning of time.
During and after WWII there were unidentified objects appearing over facilities dealing with nuclear weapons. It looks like they were concerned that we might destroy ourselves and our planet.
Over the years their stealth technology advanced so that now we only occasionally are able to detect their presence. But make no mistake they are still their keeping watch, and it would be nice to know why.