A couple of folks sent this one in.
On Friday, May 16 2008, a brand spanking new Airbus 340-600, one of the largest passenger airplanes ever built at the time, sat in its hangar in Toulouse, France without a single hour of airtime.
Enter the flight crew of Abu Dhabi Aircraft Technologies (ADAT) to conduct pre-delivery tests on the ground, such as engine runups, prior to delivery to Etihad Airways in Abu Dhabi.
The ADAT crew taxied the A340-600 to the run-up area. Then they took all 4 engines to takeoff power with a virtually empty aircraft. Not having read the run-up manuals, they had no clue just how light an empty A340-600 really is. The takeoff warning horn was blaring away in the cockpit because they had all 4 engines at full power.
The aircraft computers thought they were trying to takeoff but the aircraft had not been configured properly (flaps/slats, etc.). Then one of the ADAT crew decided to pull the circuit breaker on the Ground Proximity Sensor to silence the alarm. This fools the aircraft into thinking it is in the air. The computers automatically released all the Brakes and set the aircraft rocketing forward. The ADAT crew had no idea that this is a safety feature so that pilots can't land with the brakes on.
Not one member of the seven-man Arab crew was smart enough to throttle back the engines from their max power setting, so the $200 million brand-new Aircraft crashed into a blast barrier, totaling it.
Snopes said it was mostly legit, so I'm going with it.