Spotters descend on airports, air shows and museums, sometimes spending thousands of dollars to photograph planes’ unusual paint jobs, registration numbers–or every Delta DC-10 ever made. The most avid trade or sell their best original slides at airline photo conventions around the world. In southern Florida–where strong sun allows year-round sightings–zealous spotters have cut holes in airfield fences for a better view. And so popular is the hobby in England that a Leicester company now exists for the sole purpose of selling spotting tours. “Once you get started in it, you’re stuck,” says Aerotours founder George Pick. “You’re in your own world.” Uh-huh: 30,000 feet up.