https://www.metabunk.org/nyt-gimbal-video-of-u-s-navy-jet-encounter-with-unknown-object.t9333/
They claim that the Gimbal video is the apparently single engine of a jet aircraft at distance; it looks nothing like it. Gimbal video appears to be a circular object seen in perspective (an ellipse), with a central axis suggesting radial symmetry. To get the apparent size for comparison, you would see the rest if the aircraft at that range, visually, too; it's not there, they apparent!y didn't get a visual on a jet. Seem to know it, because they waffle back to the reflection explanation! Then, the c!aim is that Gimbal object only turns when camera does; no, the horizon doesn't change.
Note that we don't actually have any pilot testimony to go with the GIMBAL clip; no-one knows what the pilot actually saw with his eyes, if anything. One theory is that this clip was deliberately taken to demonstrate the effects of rotation on an ordinary infra-red trace as the plane turned.
The only person who suggests that this might be an 'internal reflection' is an ex-pilot, someone who admits he hasn't worked with FLIR, but who doesn't think this is a real object. This tends to reinforce my opinion that pilots aren't always the best people to interpret these clips. This probably
was a real plane of some sort, in the far distance, moving away; it would appear to be more-or-less stationary if seen by a stationary observer, but of course
a/ the 'plane taking the footage was actually moving quite fast, along a curving path
and
b/ the FLIR camera was looking sideways while tracking the object.
This causes a parallax effect, making the object appear to move fast above the clouds, but in reality it is the combination of the movement of the plane and the tracking of the camera that causes the effect.
The elliptical shape of the trace appears to be an artifact of the system; here's a plane showing two elliptical traces for comparison- note how the ellipses rotate quite independently of the plane, therefore cannot be connected
at all to the actual shape of the source.