From the early days of aviation, air carriers have transported property. Until about five years ago, property transportation other than mail was called "air express" and commanded premium rates. What is presently known as "air freight service" was inaugurated in the latter part of 1944. It is this present air freight service that is generally meant when the term "air cargo" is used. The differences between the present air freight and air express services are not extreme. Essentially, the air express service is intended for the movement of small shipments, and the air freight service is intended for the movement of considerably larger shipments. Twenty-five pounds constitutes approximately the breaking point between the two services. Ground handling for air express is usually somewhat more expedited than for air freight. Once turned over to the airline, both air freight and air express are likely to receive quite similar treatment. The minimum shipment acceptable for air freight is twenty-five pounds, and smaller shipments must still pay for twenty-five pounds. For such a shipment, the air freight rate will be about half the air express rate, but the air express rate will include pick-up and delivery while the air freight rate will apply from airport to airport only. Transportation of freight between city and airport will involve an additional charge of about fifty cents per hundred pounds at each terminal. For bigger shipments, the price difference between air express and air freight is still larger. For shipments of a hundred pounds or more, the rate by air freight may be no more than a third of the rate by air express and is quite often less than one-third. I