Of all the planes that flew the Berlin Corridors, only those of the 7405th asked to be allowed to navigate on their own, following routes that were different than other aircraft, routinely wandering 500 feet from their assigned altitude, and making random flight patterns.
The deviations were carefully noted on the ground. Furthermore, both the Russians and East Germans took their own telephoto pictures of the ambling aircraft at below the 10,000-foot maximum altitude that clearly showed open camera doors. And it couldn’t have taken counterintelligence specialists at Templehof Airfield long to conclude something suspicious was going on when as many as fifteen men emerged from one of the planes, had lunch, then climbed back into the plane and left to return to West Germany – without delivering a single passenger or cargo, or leaving with them. The “cover” was so obviously transparent that the crews called themselves the “Berlin for lunch bunch.”
Excerpt from “By Any Means Necessary,” by William E Burrows, (p189-191).