On September 29, 2006, a Gol Transportes Aéreos Boeing 737-800 collided with an ExcelAire Embraer Legacy 600 over the state of Mato Grosso, leading to the loss of 154 lives in what was, at the time, the deadliest air disaster in Brazilian history.
The Legacy aircraft's transponder was found to have been off from 54 minutes before the time of the crash until 3 minutes after, when the crew turned it on again.