In 1977, NASA performed the first free-flight of Space Shuttle 'Enterprise,' with the boat-tail extension in place, later used while ferrying mission-completed shuttles, piggyback, on NASA's dedicated Boeing 747 mother ship, back for recycling.
As the mother ship flew an arc, the ballistic fasteners holding Enterprise to the 747 were detonated, allowing the Boeing to fly out from underneath Enterprise.
NASA claims that the boat-tail reduced drag enough to double flight range. Not a bad hat trick!
We have a retired military / commercial pilot that comes in from time to time. He flew the 'flying saucer' Lockheed Super Constellations off the borders of our commie friends, stealing frequencies to be used for electronic countermeasures.
Even with Westinghouse's attention to the 'Martian' aerodynamic radar fairing, the elevator and vertical stabilizer still experienced 'challenging' turbulence - induced handling.
Roger was pretty certain that the 747 would be 'unflyable' without the tail.
Terrific fuel penalty as well.
