Complex sentence: Contrary to popular belief, the flight number is not encoded in the licence plate on the carrier tag: the licence plate is an index number linking a bag to an associated message sent by a carrier's Departure Control System to an airport's Baggage Handling System.
Split into simpler sentences: Contrary to popular belief, the flight number is not encoded in the licence plate on the carrier tag. The licence plate is an index number linking a bag to an associated message sent by a carrier's departure control system to an airport's baggage handling system.