When I was spotting from the Terminal at DEN this month, I noticed a UAL airbus 320 about to push back (loaded) and there were 3 people doing something to the nose. since the Nose was close to the terminal window I had a good view and even got some photos of it.
They were applying some kind of tape to the very tip of the nose cone. when they walked away I could see it. It was clear because you could still see the United rainbow-colored stripes but it looked like some kind of patch. And then, the jet was pushed back and headed out to the runway.
why would they do this? What does the tape do? I bet it didn't give the passengers a good feeling seeing the plane leave with a taped up nose!