The European Space Agency's Ariane 5 rocket launch on June 4th, 1996, ended in disaster just 40 seconds after takeoff due to a coding bug. The guidance system converted a 64-bit floating-point number to a 16-bit signed integer, causing an overflow error that the main computer misinterpreted as real navigation data. This led to a series of catastrophic events, including the rocket tearing apart and triggering a self-destruct mechanism worth €500 million. The code was not necessary after takeoff and was only part of the launch pad alignment process, but it ran for an extra 40 seconds due to design decisions that prioritized saving time over catching errors.