A 'snap-up' intercept is where the fighter is level at a high speed and uses its momentum to snap-up, climb steeply, to aim at a target at a much greater altitude.  The F-106 used radar snap-up attacks with all-aspect armament loads to exploit enemy targets.

Project Ice Cube was a high-altitude "snap-up" intercept evaluation conducted by F-106A interceptors stationed at George Air Force Base in 1962 (approximate date) to determine the ability of the F-106 to intercept and destroy extremely hi-flying aircraft.

The F-106 pilots (then) were outfitted with capstan partial pressure suits. They flew a full-afterburner profile to approximately 45,000 feet, accelerated to Mach 2.0 or greater, acquired the high flying target (Lockheed U-2 aircraft), initiated a high-G pull-up once they were locked onto the target with their radar, and climbed until “simulated launch” of the MB-1 nuclear rocket weapon.

During the “pop-up”, they experienced “afterburner blow-out” at about 65,000 feet, and engine “flame-out” at about 72,000 feet. When the engine quit, their pressure suits inflated, and they experienced nearly uncontrollable flight. When the nose finally dropped below the horizon and the airspeed began to climb, they regained marginal control of the aircraft. However, flying the aircraft with a fully inflated pressure suit proved to be extremely difficult. After descending to about 25,000 feet, the pilots initiated an “air start” on the engine, hoping like hell that it re-lit.

All of the F-106 “Ice Cube” flights were successful in restarting the engine, and approach and landing was without incident. Nonetheless, the “snap-ups” were all planned to occurred near-or-over Edwards Air Force Base in California, where there were long runways and ample “dry lakes” to land in the event a “dead stick” landing was required.

The “Ice Cube” tests proved the “reasonably effective” ability of the F-106 to intercept and “kill” an extremely high-flying hi-speed aircraft, although intercept conditions needed to be extremely precise.

I flew on about four of these test missions, could see the “curvature of the earth” at maximum altitude, and witnessed the totally black sky above with stars during the daylight missions. It was awesome, and one of the greatest thrills of my flying career.

Colonel Paul A. Seymour, USAF (Ret)