Way back in Nov 2006, southern Afghanistan. Waiting to go out on a patrol, I was calibrating the SOPHIE hand held thermal viewer (due to thermal cross over as we had been delayed leaving until well after dark). For some reason something caught my eye, and looking up I can only describe the shape as looking like a cross between BAEs Teranis UAV (
https://www.baesystems.com/en/product/taranis) and a B2/ F117. It had rectangular shaped solid white (hot) shapes around the outer edges, when viewed through the thermal spectrum. With the naked eye, there was nothing visible. And it was absolutely silent, I did give the sight to another person who saw it cruise away from us and confirmed that he saw something but would not be able to confirm the shape or what it was. Altitude wise, id have a guess at around below 5000ft AGL so below 8000AMSL. It was very strange.