Ariane 5 Flight 501 Failure

Flight 501, which took place on June 4, 1996, was the first test flight of the Ariane 5 expendable launch system. It was not successful. Due to a malfunction in the control software the rocket veered off its flight path 37 seconds after launch. It was torn apart by high aerodynamic forces which caused the onboard computer to trigger self-destruction.
The breakup caused the loss of the payload: four Cluster mission spacecraft, resulting in a loss of more than $ 370 million.
It is one of the most famous computer bugs in history.

The Ariane 5 software reused the specifications from the Ariane 4, but the Ariane 5's flight path was considerably different and beyond the range for which the reused code had been designed. Specifically, the Ariane 5's greater acceleration caused the back-up and primary inertial guidance computers to crash, after which the launcher's nozzles were directed by spurious data. Pre-flight tests had never been performed on the re-alignment code under simulated Ariane 5 flight conditions, so the error was not discovered before launch.