Darn, I can't find the link at the moment - but months ago I saw an amazing photo on the Petapixel blog in which a photographer shot every plane that landed at ?Airport? in a day then composited all the planes into one image. Which made me wonder if it could be done with video? It turns out that it definitely can be done but is easiest with a pure blue sky and with the camera facing up not toward the horizon. With an even blue background it's fairly easy to key out each airplane and put them together. The bridge in this shot is an added time lapse under the 1st Street bridge in San Diego.
I was really surprised by two things: the number of planes that landed in 4 hours (close to 70) and the dominance of Southwest Air.