sentences:  According to CENIPA, the air traffic controllers contributed to the accident by originally issuing an improper clearance to the Embraer, and not catching or correcting the mistake during the subsequent handoff to Brasília Center or later on.CENIPA also found errors in the way the controllers handled the loss of radar and radio contact with the Embraer.CENIPA concluded that the ExcelAire pilots also contributed to the accident with, among other things, their failure to recognize that their transponder was inadvertently switched off, thereby disabling the collision avoidance system on both aircraft, as well as their overall insufficient training and preparation.