An Auxiliary Power Unit, commonly referred to as APU, is a small turbine engine usually located in the tail section of an aircraft. Unlike the main engines that provide thrust for flight, the APU is designed to provide energy for functions other than propulsion.

"We can say with a high level of confidence is it doesn't appear to be a mechanical issue with the Boeing fuel control unit," Bedford told reporters on the sidelines of an air show, adding FAA employ...