Wikipedia
WorldTracer is a SITA / IATA service provided for the tracking of lost or delayed baggage. It has been in operation for many years and is used by airlines such as Qantas, Lufthansa, and Emirates. The system allows for the rapid determination of mishandled baggage.
WorldTracer operates globally and can exchange information with 2800+ member airports. It tracks and follows baggage for up to 100 days and collaborates with other services. The World Tracer internet interface allows passengers to track their bags by entering a transaction number.
Whenever baggage is found without an owner, it can be registered as on-hand baggage. It is then automatically matched with various missing-baggage files (called AHLs). Whenever an on-hand produces a likely match, the station that registered the missing baggage receives an alert. The bag is matched based on its routing number, tag number, passenger's surname, type of baggage and content. When a handling agent finds an on-hand which matches one of AHLs, he/she can request the on-hand by sending a message to the station that registered it.
The tracking number format is AAABBNNNNN, where AAA is the airport's IATA-Code, BB is the airline's IATA-Code and NNNNN is a 5-digit tracking number. For example, the tracking number PHLDL19676 is from Philadelphia International Airport, flew on Delta Airlines, and has the tracking number of 19676.