Brian J. Duddy
In the early days of jet fighters, the U.S. Air Force acquired both the F-102 and F-106, two different aircraft that look remarkably similar. But a closer look, particularly at the fuselage shapes, reveals a subtle yet significantly important difference.
Performance wise, that difference in shape allowed the F-106 to be a more successful design and more effective and suitable for USAF missions. The design principle that distinguished the F-106 was the application of a theory called “Whitcomb’s Area Rule”, named after Richard Whitcomb, an engineer with the National Advisory Committee for Aeronautics (NACA) – the forerunner of the National Aeronautics and Space Administration (NASA.)
Whitcomb’s aerodynamics research allowed a generation of jet aircraft to more easily exceed the speed of sound and deliver to the Air Force the performance it was after to intercept Soviet bombers.
Get the full story of this breakthrough in aircraft design and see additional photographs at Flashback: Convair’s F-102 and F-106 – Aren’t They Really the Same Airplane?
Richard Whitcomb, National Advisory Committee for Aeronautics (NACA) engineer with wind tunnel model of the F-102. In the early days of jet fighters, the U.S. Air Force acquired both the F-102 and F-106, two different aircraft that look remarkably similar. (NASA Photos) 
Convair’s “Delta” aircraft. From top: F-102, F-106 and B-58. (Courtesy Image) 
In the early days of jet fighters, the U.S. Air Force acquired both the F-102 and F-106, two different aircraft that look remarkably similar. This image shows a side-by-side comparison of the Convair aircraft. The F-106 is on the left.