Since the advantage of air freight is much shorter transit times, cargo must move quickly through an airport. The time for cargo operations depends on four factors: customs clearance procedures, cargo inspection procedures, the efficiency of cargo handlers, and the layout of storage facilities.
For imports the customs procedures are critical. The clearance requires both the airway master bill, sent at the time the flight departs, and the customs declaration, filed by the brokers after the cargo had been shipped. In some countries the customs authority at the airport uses the same procedures and systems as at other international gateways, and inbound cargo can take up to a day to be cleared. In others the procedures are adapted to the requirements of air cargo, with all transactions conducted electronically and cargo cleared within one or two hours on a 24/7 basis.
The demand for air freight is limited by cost, typically priced 4–5 times that of road transport and 12–16 times that of sea transport. Air freight rates generally range from $1.50–$4.50 per kilogram, while the value of air cargo typically exceeds $4.00 per kilogram. Commodities shipped by air thus have high values per unit or are very time-sensitive, such as documents, pharmaceuticals, fashion garments, production samples, electronics consumer goods, and perishable agricultural and seafood products. They also include some inputs to meet just-in-time production and emergency shipments of spare parts.
Demand for air freight exports has been limited from landlocked developing countries because most enterprises ship small volumes of low value goods. The main exports shipped by air from developing countries are cut flowers, electronic parts, and fresh fruits and vegetables. Imports by air typically include high value consumer goods. However, without a significant outbound flow, the inbound air freight rates are higher — reducing the types and quantities of goods transported by air.