The procurement process in the aviation industry is similar to the procurement process in other major industries. It begins with the requisitioning process which is communicated to the supplier using a purchase order (PO). There are several ways to identify supply needs. Initial provisioning using the recommended spare parts list (RSPL) or the initial provisioning list (IP) is common for preparing a purchase request. The RSPL is a list of recommended spare parts that manufacturers of airplanes recommend; the IP is a similar list but only includes critical spares according to operational requirements. Companies may also have need-based demands which is when a spare part is needed and out of stock. A company may need to procure an item for replenishment action, which is the act of re-stocking low-cost parts when they reach a certain level. The needs identified are communicated to the purchasing department and they create a purchase request (PR), where delivery is scheduled, quality parameters are defined, and the request is authorized or rejected.