Synopsis The two aircraft collided at Flight Level 370 on Airway UZ6, travelling in opposite directions. Both were relativey new aircraft, indeed the Legacy was on a delivery flight, and both were equipped with late-model TCAS anti-collision equipment, which apparently did not function. The aircraft were at the boundary between two ATC en-route centers, Brazilia and Manaus, and were talking to two different controllers. However, both radio and radar contact had been lost with the Legacy at the time of the collision. It later transpired that the software at the control center controlling the Legacy had automatically changed the Legacy's cleared flight level to that of its flight plan when it passed a waypoint, although the Legacy had lost radio contact at the time and continued flying at its last cleared Flight Level. The U.S. National Transportation Safety Board has published a Factual Statement on the accident. Unfortunately, legal proceedings started almost immediately after the accident, and the Legacy pilots, who are U.S. citizens, were detained in Brazil until the detention was annulled by a Federal judge in December 2006. As of writing (August 2007), there seems to be a good chance that they will be formally charged with and tried for unlawful killing. Although we normally do not take a position on such issues in this compendium, we feel strongly, along with many aviation organisations, that the causal investigation must be completed before criminal proceedings are considered. Jörn Stuphorn of Causalis Limited has prepared a Why-Because Graph of the accident from the public information (mainly news reports in trade journals). Here are the slides from the talk he gave on his Why-Because Analysis at the Ninth Bieleschweig Workshop in Hamburg in May 2007.