On the night of Monday, 1 July 2002, BAL Bashkirian Airlines Flight 2937, a Tupolev Tu-154 passenger jet, and DHL International Aviation ME Flight 611, a Boeing 757 cargo jet, collided in midair over Überlingen, a southern German town on Lake Constance, near the Swiss border. All of the passengers and crew aboard both planes were killed, resulting in a total death toll of 71.
In this video you will see the investigation taken place after incident and the responsible factors which lead to the disaster.
Air Crash Investigation.