Weird transparent UFO spirals down over Brooklyn 24-Sep-2021

This daytime UFO sighting was filmed in the sky above Brooklyn on 24th September 2021.

Witness report: Me and my wife where at the rooftop enjoying the afternoon weather when a bright flash in the sky caught my eye. I looked up but couldn’t see anything. I mentioned to my wife, and as we looked up we both witnessed the flash again and what appeared to be a shape. The building is in Brooklyn and the object was spotted south of La Guardia Airport.
First I thought of a flock of birds but where too high, and move too fast and coordinated. At times looked like a cloth or a transparent flag, but the flight path seemed oddly smooth and unpredictable.
Because of looking almost transparent it’s hard to say, but seemed to spiral down in a controlled way. It appeared to be a physical object that reflected the light of the sun only at certain angles when turning. Other than those moments where the sun reflection flashed, it was very hard to see it at all.
My wife started filming it and I ran to get the binoculars, when I got back the object was gone. My wife filmed it around 25 seconds after I first saw it so it’s all there in the video.
It felt it was high and large, but is very hard to say exactly what we saw, even watching the video is hard to make our minds on what could have been. It could be some natural phenomena, but a strange one at least.