Semitransparent triangular craft with large white bright spheres on each of the three corners

While on my daily walk at about 1:08 pm, an object in the sky caught my attention flying SE. At first, I thought it was the experimental aircraft from the local airport, minus the very loud sound it usually makes. A couple of seconds later, I realize that it is not the experimental aircraft that I often see in the area when it started to rotate about the x-axis as it flew in a straight line. The craft rotated +/- 180 degrees, back and forth, and still maintained its SE heading. I quickly got a glimpse of the structure of the craft when it rotated. It looked like a light gray "T" structure with the bright white sphere at each end of the "T". Then a semitransparent "film", if you will, formed the triangular shape of the craft, encompassing the "T" structure. No apparent form of propulsion and it traveled faster than a commercial airplane. It disappeared over the horizon in about 10 seconds from the time I noticed it. I couldn't tell whether or not it emitted a sound as I was next to a busy street. No other witnesses on foot in the area. A jet liner was flying above the craft in question headed in a SE direction also. A small aircraft in the area headed W should have seen the craft as it headed towards it.