The concept is simple: shoot the individual planes flying across a pure blue sky, then chroma key the blue out as if it’s a green or blue screen leaving only the plane behind. Then put them all together on a video timeline. I did some tests and discovered that it didn’t work well if there were trees in the edges of the frame so scouting good locations took the most time. I watched the weather for a cloudless day then sat in a park and shot every plane that flew over. I locked the camera (Canon 7D with a EF-S 17-55 f/2.8) on a tripod and shot the planes with 1080p video at 24fps with an exposure I’d tested the day before (50/s, f/13, ISO 100) that would keep the sky deep blue with no blowout for a good chroma key.
To give the video a sense of temporal change as the planes fly by I did an 8 hour time-lapse under a bridge nearby shot at the same angle and composited it over the planes. Without it there’s no sense of time passing. I used an intervalometer to shoot about 800 images with the same exposure as the video. Once I had it posted as a regular video clip, I keyed the sky out of it as well. I put everything together in Adobe Premiere, which challenged my system since I needed 40 video tracks to stack all the airplane clips together. The last piece was to put a new sky back in — a still image with depth and clouds that’s panned using key frames in Premiere.
Read more at http://www.petapixel.com/2012/12/01/five-hours-of-airplane-landings-captured-in-thirty-seconds/#s5LdvWrWwRlcHtk0.99