On the Exact Calculation of the Fill Rate for Repairable Parts: Application to an Airline Company

Abstract

This paper focuses on the improvement of inventory policies of repairable parts of the airline company Air Nostrum. The company uses the sales replacement policy to manage their repairable parts and the base stock is determined by means of an approximated expression of the fill rate assuming Poisson distributed demands. However, this paper shows that real data may not always be modelled with the Poisson distribution and the only exact method available in the literature fall into significant deviations when other discrete distribution is used. According to that, this paper derives an exact method to compute the fill rate in the presence of any sta-tionary, discrete and i.i.d demand pattern for the policy the company uses. Illustrative examples show that deviations which arise from using approximate methods can lead to overestimate the fill rate so the inventory policy does not reach the target fill rate.