Minimizing user inconvenience and operational costs in a dial-a-flight problem for flying safaris.

We study a Dial-a-Flight Problem faced by one of the major safari airline companies in Tanzania. Given a set of daily passenger requests and a fleet of heterogeneous airplanes, the problem requires to determine the best set of itineraries to transport the passengers from their origins to the requested destinations within specific time windows, while satisfying a number of operational constraints. The aim is to minimize user inconvenience, measured by delays with respect to the pre-defined time windows and by the number of intermediate stops in the itineraries, and operational cost. The problem is complicated by the high number of daily requests in peak touristic periods, and by the fact that refueling is possible only at a limited number of airstrips. We solve the problem by means of an adaptive large neighborhood search, which we enrich with local search operators and a set partitioning model. Extensive computational tests on real-world instances prove the effectiveness of the proposed algorithm, which can improve the solutions found by the company both in terms of operational cost and user inconvenience, in reasonable computational time.