Correctly positioning and buffering inventory can help you create a more flexible supply chain with lower costs.
In the military, it is common practice to pay suppliers on a "cost plus" basis. Effectively, this makes all the suppliers a "make to order" location. That is, the suppliers can only make product when there is a firm order. There is no mechanism for the supplier to make product in advance, sit on safety stock, and provide faster service.
Keeping helicopters flying is not trivial. They are made up of many parts and operated in tough conditions. Many of the key parts(drive shafts, sycn shafts, blades) require many sub-components and must be made with specialized materials in a high-precision manufacturing environment.
The supply chain for these key parts can be very long (measured in many months), and it is expensive to keep enough of these items around as spare parts.
With the current system, each key part had to either be stored in inventory as safety stock (waiting to be needed) or the the military had to wait for the supply chain to produce another (creating a backlog of demand and a helicopter that was grounded). Neither alternative was great.
A better solution is to optimize the placement of strategic buffers in this supply chain. The chart below on the left shows the existing supply chain. The yellow box on the right represents the customer (the military) and a key part. The gray boxes to the left represent all the steps in the supply chain needed to make this particular part. You can see the complexity of the supply chain. In the baseline, the entire buffer is held by military, represented by the red bar.
In the optimal case, the suppliers hold buffers. These buffers are seen by the red bars. The inventory optimization identifies where and how big these buffers should be. Now, the military can keep the helicopters flying with much less money tied up in working capital (or worse, with many helicopters not being able to fly).
Of course, implementing this solution is not trivial. Contracts with the suppliers have to be re-worked to allow them to create and maintain the safety stock buffers.