Lufthansa's optimizer reschedules aircraft, crew and passengers together after delays.

Airlines face disruptions constantly: weather, air-traffic control holds, aircraft faults and crew unavailability. When a flight is delayed, the airline must re-plan not only the aircraft but the connecting passengers and the crews, and the traditional answer is to let each department fix its own part.

In 2019 Lufthansa and Google began a five-year collaboration to apply operations research to operational schedule recovery. Their Operations Decision Support Suite (OPSD) jointly optimises over aircraft, passengers and crew, rather than handling each in isolation.

Solving this jointly is hard at airline scale, so the team developed novel decomposition techniques and heuristics to make it tractable. The service is in daily use by Lufthansa subsidiary Swiss International Air Lines, having saved EUR 12 million and 14 ktonnes of CO2, and is being deployed across the whole Lufthansa Group.

The project marks the point where the industry stopped treating aircraft recovery, passenger recovery and crew recovery as three separate puzzles and viewed schedule recovery as one integrated optimisation problem.