Passenger plane use the spare volume while in the plane's baggage hold (the "belly") that is not being used for passenger luggage—a typical exercise employed by passenger airlines, who Furthermore transport cargo on scheduled passenger flights. Cargo can be transported within the passenger cabin as hand-have by an “on-board courier”. https://arthurwcahy.wikiannouncement.com/6084123/5_simple_techniques_for_air_freight_australia