Each suit is sized individually, although most suits can be worn by astronauts of different heights. No ACES has failed during normal flight operations. The "Columbia" investigation found that the crews' ACES all failed at some point, but also that none of the "Columbia" crew had sealed their helmets, and also that several were not wearing suit gloves. By comparison, in 1966 an SR-71 pilot in a similar suit, whose helmet and gloves were sealed, survived similar pressure conditions when his aircraft broke up while flying at approximately Mach 3. The "thermal and chemical environment of the "Columbia" accident (the temperature and oxygen concentration) was "much more severe" than in the SR-71 accident, however, and the report recommended that future crew survival suits be evaluated for thermal and chemical resistance as well as (as USAF suits had been evaluated previously) pressure and windblast.