Columbia Crash
It cost NASA $13 billion with the 2003 Columbia crash that claimed the lives of seven astronauts. Unfortunately, the spacecraft’s external tank lost a piece of foam and breached the wing while trying to re-enter Earth’s atmosphere.
The huge mistake done by NASA was that 16 days before the accident, they saw the same falling foam issue and didn’t fix it. The tragic accident led to NASA retired their space shuttle fleet in 2011.