Pretty sure whatever that is, it's on the ground. Even though the longer (more distant, over the engine nacelle) shot is relatively short, notice the UFO seems to stay in the same spot relative to both the a/c and ground. That tells me it's not moving. This would have been much more obvious had the video lasted longer, which is why I think we saw only such a short clip.
As to what that is, I'd guess maybe stadium lights or reflections off something like a large solar farm. Of course all primary data that would allow us to figure out what it is is conveniently not included. For example, had the date/time of the video and flight number been provided, it would be a simple matter to go back and look at the actual flight track on Flightradar24 and get a reasonably accurate location of the a/c. With that we could scour Google Earth see what's on the ground.