How many USAF pilots died because of the F-104's downward-firing ejection seat?

Early Starfighters used a downward-firing ejection seat out of concern that an upward-firing one could not clear the aircraft's T-tail. The fighter flew too fast for pilots to clear the tail assembly if ejected with conventional upward-firing seats. The mechanism was complex and included metal "spurs" on the heels of the pilot's boots, which locked onto steel balls on the footrests.

Twenty-one USAF pilots failed to escape their damaged aircraft in low-altitude emergencies because of that seat. Twenty-one test pilots died using those seats, among them Korean War ace Iven Carl "Kinch" Kincheloe Jr. On July 26, 1958, Kincheloe ejected at low altitude from an early-model F-104 at Edwards Air Force Base: the ejection seat threw him into the ground before his parachute could slow his descent.

The downward-firing seat was replaced by the upward-firing Lockheed C-2, which could clear the tail, though it kept a minimum speed limit of 90 knots. Many export Starfighters were later modified with Martin-Baker Mk.7 "zero-zero" seats, usable at zero altitude and zero speed.