I was in the West Village yesterday afternoon when I saw this writing going on in the sky. It was part of a work of art called "The Sky Is The Limit/NYC" by Kim Beck. The air was so dry and the subsidence so great that I suspect the skywriting disappeared a lot quicker than the artist wanted it to.
I took a bunch of photos so I could make an animated gif. That image is after the jump so readers don't have a seizure here.