The traditional operating theory of postal transportation is relay transmission.FEDEX International ExpressMost companies use central allocation theory or turntable allocation theory to organize global networks. To put it simply, the express company sets up a distribution center (Hub) in the central area according to the actual situation of its own business. The express mails collected from all over the place are distributed according to the destination area and loaded on the plane. Airplanes from various places flew to the distribution center that night, exchanged express mails and flew back. In the early morning of the next day, the express mail was delivered to the recipient's desk by a car from various branches. This method seems unreasonable, but because the central distribution theory reduces intermediate links, the flow of express mail is simple and clear, reduces errors, improves operating efficiency, and shortens delivery time. It has been proved to be economical and effective.