It turned out that even laborious hooting and scooting weren't enough. Spies had learned that the Soviets had a drawing of an OXCART plane—obtained, it was assumed, via an infrared satellite.
As a plane sat in the hot desert, its shadow would create a relatively cool silhouette, visible in infrared even after the plane had been moved inside.
"It's like a parking lot," Barnes told National Geographic News. "After all the cars have left you can still see how many were parked there [in infrared] because of the difference in ground temperatures."
To thwart the infrared satellites, Area 51 crews began constructing fanciful fake planes out of cardboard and other mundane materials, to cast misleading shadows for the Soviets to ponder.
Find out more about the cat-and-mouse game at Area 51 in this article from NatGeo News. Link -Thanks, Marilyn!
(Image credit: Roadrunners Internationale via Pangloss Films)