On May 21, 2009, at 2147 EDT, an Airbus A330-200, Brazilian registration PT-MVB, operated by TAM Airlines as flight 8091 from Miami International Airport, Florida, to Sao Paulo Guarulhos International Airport, Brazil, experienced a loss of primary speed and altitude information while in cruise flight at FL370. Initial reports indicated that the flight crew noted an abrupt drop in outside air temperature and observed St. Elmo's Fire, followed by the loss of the Air Data Reference System, disconnections of autopilot and autothrust, and loss of primary airspeed and altitude. The flight crew continued using backup instruments, and after approximately 5 minutes, primary data was restored. The airplane remained in alternate flight law and displayed a rudder travel limit flag. The crew determined they could not restore normal law and continued the flight under the appropriate procedures. The flight landed at Sao Paulo with no further incident and there were no injuries or damage.

With the concurrence of the Brazilian Centro de Investigação e Prevenção de Acidentes Aeronáuticos (CENIPA), the NTSB initiated an incident investigation into this event.

The final report for this incident was combined with and can be found under NTSB investigation number, DCA09IA064.