Air freight, also known as air freight, is an important part of modern logistics, providing safe, fast, convenient and high-quality services. The traditional air freight business is mainly trade goods, and it is stipulated that the volume of each cargo should not be less than 5 * 10 * 20cm. Postal services are mainly private letters, and each package is required to weigh less than 20kg and the length is less than1m.. The receiving scope of air express mainly includes two categories: documents and parcels. Among them, documents mainly refer to business documents and various printed materials. For parcels, the gross weight is generally not more than 32kg (including 32kg) or the single side of the outer package is not more than 102cm, and the sum of three sides is not more than 175cm. With the fierce competition in the air transport industry, in order to attract more customers, express delivery companies often relax the requirements for package size.