# Development of a Maintenance and Spare Parts Distribution Model for Increasing Aircraft Efficiency
## 2 Materials and Methods
### Methods
#### 2.2.3 Distribution Network Design and Management  
Distribution logistics includes all storage and transport activities of the distribution of goods to the customer and control and inspection activities [24]. It is the link between the entrepreneurial production logistics and the customer's procurement logistics [25]. Distribution logistics is a key driver of the overall profitability of a business because it affects both the supply chain cost and customer service [26]. The goal of distribution logistics is to ensure the physical availability of products and associated flow of information [27] to achieve a high delivery service while ensuring minimal distribution costs and trying to acquire new customers. The delivery service goal can be subdivided into delivery time, reliability, integrity, and flexibility [28]. On the other hand, the distribution costs include storage costs, transport costs, costs of holding capital, administrative costs, and out-of-stock costs [29]. The fundamental goal of the distribution logistics is to achieve the best possiblebetween distribution performance and costs [27]. In the past, the main focus was operational and tactical problems; however, to manage logistics with success in the future, it is also required to have active strategic planning [27]. The design of a distribution network determines the potential performance and the cost structure in the long term of the logistics network and there are different frameworks that can be used to design a distribution network [27]:  
* New design or re-design.
* Structure-oriented, i.e., based on the choice and quantity of locations; or resource-oriented, i.e., based on when the production, warehouse or transport capacities change.
* Static or a dynamic design.
* Cost efficiency vs. responsiveness.
* Centralized vs. decentralized.
* \"Push\" vs. \"pull\".  
The processes in a supply chain are divided into two categories depending on whether they are executed in response to a customer order or in anticipation of customer orders. \"Pull\" processes are initiated by customer orders, whereas \"push\" processes are initiated and performed in anticipation of customer orders and are normally based on demand forecasts. This dilemma is important when considering strategic decisions related to supply chain design [26].  
The distribution network of a company depends on the number of different storage levels, the number of warehouses at each stage, and the spatial distribution of warehouses [24]. The optimal number of storage levels within the distribution structure depends on the company and customer structure, since the means of each storage stage generates additional capital commitment and fixed costs, but in return the delivery service increases [30]. However, the goal should always be to keep the number of stages as low as possible to minimize the stocks in the factory and distribution warehouses, but without deteriorating the delivery and service levels to customers [27].  
In terms of distribution logistics, various approaches can be used for the transportation of goods to customers. The advantage from one option in comparison with the others depends on the company and customer structure. The network characteristics should be decided on a case-by-case basis, and for that the typical logistics approaches for distribution networks include direct delivery, central warehouse delivery, the \"milkrun\" concept, transshipment points, cross-docking (one stage), and cross-docking (two stages) [31].