Since 2011, when we first initiated a digital and lean transformation effort in Thenamaris Marine Personnel Department, the Crew Scheduling System (jointly developed with Best Practice Consulting) has become the core system and a single point of reference for various groups of business users and partners. It is simple, as it offers to any user, even those with least ‘IT literature’, the opportunity to visualize or interact with the plan and make optimal scheduling decisions. It is lean, offering a variety of structured workflows related to seafarers’ pre-embarkation processing, certification, dispatch and performance monitoring. Most importantly, it integrates a powerful optimization engine developed with mathematical programming techniques (MILP) which proposes the optimal schedule over any fleet cluster and planning horizon, by considering a large set of business constraints.