The Belgium flurry of sightings were almost all triangular UFOs, which suggests that the triangular ones are *not* "ours".
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The assumption, inferrence is not necessary at all, imho.
35+ years ago my relative insisted that our craft could go virtually or literally instantly to any spot on the globe either under computer control or piloted.
I personally don't know whether ALL triangle craft are ours, or not. I just heard John Lear say so. He has a lot better connections than I do.
But our craft have been roaming unfettered over the entire globe for decades. Some say to the moon and Mars besides.
And yet, they decided to converge on Belgium back in the 1980s...