Sphere with reflective rectangles on floating past/below airplane as I flew from England to Scotland

Flying from Luton airport to Inverness on the 19th March 2022 on an easyJet flight.
I was looking out of the aeroplane all of the flight searching for wind turbines and looking at terrain changes.
somewhere near Mid flight so don’t know where I was. Looking out the window I saw a sphere shaped object float past, beneath the airplane. I’d guess 100 yards away. Hard to tell the size as perspective is difficult in an airplane but guessed 600-800mm wide. It was made from reflective material but not as shiny as a mirror reflection.
I told my family at the time but they presumed it was a balloon of some kind with helium in it that accidentally got realeases. Only saying now as in the news there’s reports of Chinese balloons being sent over America for research. Could this have been a spy balloon? or a prototype to see if it can fly undetected and then be used in a different kind of warfare??