Definition: Direct transit freight
Direct transit freight is freight, which continues its journey on the same aircraft on a flight having the same flight number as the flight on which it arrived. Direct transit freight is not unloaded and reloaded at an airport it directly transits.
On some flights, the flight number changes at an airport to designate the change between an inbound and outbound flight but with intermediate stops. An example is a flight from Barcelona to Hamburg where the flight continues to Frankfurt before returning to Barcelona. Where freight for an intermediate destination continues its journey on the same aircraft in such circumstances, it should be counted as direct transit freight.
Draft Glossary on Air Transport Statistics, 2001