Reports may be credible, but the reporting on that reporting less so. The way I understand it, some people saw some thing, FLIR saw some thing, a ship radar is claimed to have seen some things, but there's little to actually connect these observations as being
the same thing.
My current best theory is that pilots were seeing a reflection on the surface of water and got confused because FLIR had a possibly unrelated and buggy interaction between an internal reflection in optics and tracking software.
(As for the radar thing, I hear it being said that there was a radar that saw someting, but no concrete information is being presented.)
Now take it from the other way around. Say it's aliens, or supernatural beings. Then why on Earth would they behave in an exact way that makes the FLIR footage indistinguishable from a camera auto-tracking a reflection on its own optics? Why exactly this pattern?