عملیات حمل و نقل هوایی: بررسی ادبیات و مقایسه با شیوه ها Air cargo operations: Literature review and comparison with practices

۴٫۲٫۵٫ Freight forwarders’ decisions The literature has only addressed the problem of spot market demand estimation and capacity booking when a long-term contract has been made. In fact, the freight forwarder must forecast the demands for the shipments of different categories and different legs ahead of time, often a year, and then allocate the demands between a long-term contract with a discounted price and spot market orders with dynamic prices. The freight forwarder forecasts demand by integrating factors, such as trend, seasonality, and ad hoc events. Then, the forwarder allots capacity from several airlines and from the long-term contract and the spot market to maximize the expected profit under demand uncertainty and market prices, subject to transport budgets, departure time (e.g., morning or night flight), service priority, and capacity allocation from the airlines. The capacity management problem for the forwarder can be formulated as a robust optimization model because the delivery of the cargo with high priority (with very high probability) should be ensured while the demand of shippers and the capacity allocation from airlines are uncertain. ۴٫۲٫۶٫ Air cargo supply chain coordination The two most important players in an air cargo supply chain are the airlines and the forwarders. A great challenge that airlines face is demand estimation and capacity planning. An effective approach to improve capacity estimation is to make forwarders share their demand information (Hihara, 2014). However, this information sharing, without a proper mechanism to allocate the benefits, is in conflict with forwarders’ interest because it might encourage airlines to charge forwarders with high prices. Therefore, the mechanisms of information sharing and coordination between airlines and forwarders are of significant value. What complicates the matter is that in the air cargo industry, an airline usually works with multiple forwarders of a non-negligible size, and conversely, a forwarder collaborates with multiple airlines. This scenario differs from the situation in the goods supply chain literature and makes the mechanism design in the air cargo industry particularly interesting. ۵٫ Summary In this work, we reviewed the literature on air cargo operations and compared state-of-the-art theories with real-world practices. We first described the air cargo industry and then analyzed the characteristics of air cargo operations compared with air passenger operations. Then, we conducted a bibliographic survey of the literature on air cargo operations, in which we focused on studies that used quantitative models from the perspectives of airlines, freight forwarders, and the air cargo supply chain. Subsequently, we identified the key decision problems in air cargo operations and discussed the gaps between previous research and real-world practices on the basis of our literature review and in-depth interviews with airlines and forwarders. The literature has already investigated some real-world problems in the air cargo industry. Nevertheless, a number of key issues have not been adequately examined. These issues include network revenue management for airlines, low- and highdemand bundling sales, capacity allocation between long-term contracts and the spot market for forwarders, pricing strategies of airlines, and coordination among players in the supply chain. This review identified several significant gaps between the theories and practices related to air cargo operations. Operations managers commented that although theoretical models contribute significantly to the literature, some assumptions in the models often deviate from operational realities. In concluding this study, two points are noteworthy. First, numerous real-time operational information systems or decision support systems exist in the air cargo industry, and, thus, a huge amount of data is actually available from airlines and forwarders. Therefore, we expect that data-driven decision making will emerge as a key approach to solving problems arising in air cargo operations, and such applications will in turn benefit the methodological research for big data. Second, the IT infrastructure in the airline industry has long been well developed, and interconnection among different players in the air cargo supply chain is ever-increasing. The use of RFID and a cargo tracking system facilitates the increased visibility of air cargo throughout the supply chain (Gontarz et al., 2015). With such visibility and interconnection, some integrated decision models can be expected because many operational decision problems we have reviewed are closely related to one another.