<h1>Aviation security protocols: aircraft returned to gate after a boarded-passenger failed to board, baggage offloaded.</h1> Aviation security protocols required the aircraft to return to gate after a passenger whose boarding pass had been scanned failed to board; crew offloaded the passenger's hold baggage and airport security detained the individual for questioning to reconcile the mismatch between boarding records and actual onboard occupancy and to comply with required baggage and security procedures.