" One of the first things Colonel Slater did after taking command of the base was to hang a sign over the House-Six bar that listed Slip Slater’s Basic Rules of Flying at Groom Lake. There were only three rules. Try to stay in the middle of the air. Do not go near the edges of it. The edges of the air can be recognized by the appearance of ground, buildings, sea, trees and interstellar space. It is much more difficult to fly there. "

― Annie Jacobsen , Area 51: An Uncensored History of America's Top Secret Military Base