The Shuttle program operated accident-free for seventeen years and 88 missions after the "Challenger" disaster, until "Columbia" broke up on reentry, killing all seven crew members, on February 1, 2003. The ultimate cause of the accident was a piece of foam separating from the external tank moments after liftoff and striking the leading edge of the orbiter's left wing, puncturing one of the reinforced carbon-carbon (RCC) panels that covered the wing edge and protected it during reentry. As "Columbia" reentered the atmosphere at the end of an otherwise normal mission, hot gas penetrated the wing and destroyed it from the inside out, causing the orbiter to lose control and disintegrate.