This 737 Max 8 was flying a few missions from BFI shortly before I left the region. At first I figured it was just another jet that, while in Ural’s colors, was likely going to another airline and needed to be repainted. However, when it taxied by me, I noticed it had an “experimental” marking on the fuselage. Then I saw that it had some instrumentation mounted in one of the windows. Apparently, it is doing something different. No idea what it is and I probably will never know.