The F-106 was one of the star performers of the first generation of true supersonic Air Force fighters, the famed "Century Series" that included the North American F-100, McDonnell F-101, Convair F-102, Lockheed F-104, Republic F-105 and Convair F-106.

The F-106 was a derivative of the F-102 Delta Dagger, which had a troubled development and never seemed to quite live up to the Air Force's expectations for performance. Originally dubbed the F-102B, the F-106 eventually received its own designation and its official nickname, Delta Dart. To most who flew it and worked on it, however, it was simply the "Six."

Perhaps the most significant basic difference between the F-102 and the F-106 was in fuselage shape. The Delta Dagger had a somewhat bulky cross section. The Six, by contrast, had a slim, aerodynamically advanced area-rule fuselage, whose pointy cigar shape helped minimize drag-inducing shock waves at supersonic speeds.

The F-106 also featured a more powerful Pratt & Whitney J75 after-burning turbojet. Almost from its first flight in December 1956, the aircraft showed that it would easily meet the Air Force's requirements for a speed of Mach 1.9 and ceiling of 57,000 feet.

"Finally, by the end of the '50s, the Air Force had the long sought after 'ultimate interceptor' it had anticipated in the late '40s," wrote Christopher T. Carey, a historian at the McClellan Aviation Museum (now Aerospace Museum of California), in his online history of F-106 development.

The need for such an interceptor was obvious to U.S. defense officials, who were watching with concern the Soviet Union's development of faster, long-range nuclear bombers. The Six's job would be to run down such intruders, if necessary, and then destroy them with an atomic weapon of its own, a Genie nuclear-tipped rocket.

This blunderbuss approach to air defense was necessary because precision air-to-air weapons had yet to be invented. Instead, F-106 pilots were to launch their Genie toward the target with a characteristic looping motion, then flee, to get as far away as possible prior to detonation.

When it first entered the Air Force inventory, flying the F-106 was a revelation. Maximum speed was Mach 2.31 at 42,431 feet.

"Ask any pilot who has piloted the Six, and he will quite readily tell you that it was one of the best aircraft he has ever flown," Carey wrote.

Handling the delta wing felt much the same as handling more conventional designs. Plus, the delta wing gave more agility at low and intermediate speeds.

Pitch responsiveness was feather light. The F-106's reaction as it came close to stalling was predictable, beginning with light buffeting and then progressing to worse things. At that point, any increase in angle of attack would lead to severe oscillation and, in all likelihood, a flat spin.

-- Peter Grier