Commercial air travel is by far the safest transportation modality available to humanity today. It has achieved this enviable status by deploying thousands of professionals, including pilots, dispatchers, and air traffic controllers to operate very reliable air vehicles, bringing them and their passengers safely from origin to destination while managing dangerous weather, other traffic and system failures for decades. The air transportation has been undergoing undeniable and continuous progress and modernization since its inception. Thanks to advances in navigation capabilities, such as satellite-based navigation systems, aircraft can fly increasingly complex trajectories, including final approaches. The same aircraft are envisioned to fly in formation relatively soon. More daring moves include the recent introduction of "Free Flight" operations. Despite all these impressive improvements, they remain largely incremental in nature and they hit a "wall of complexity" that makes it somewhat difficult to incorporate more automation, such as the elusive, and perhaps infeasible, goal of achieving fully automated air traffic control, and to design and insert autonomous vehicles, small and large, in cities and at high altitudes.We introduce Ariadne, a thread to accelerate the productivity gains achieved by air traffic services providers around the globe. Ariadne is an engineered version of the common sense practice of always keeping a "Plan B", and possibly "plans C, D, E, and F" against unexpected events when any decision is made by pilots, air traffic controllers, dispatchers, and any other safety-critical actor of the air transportation system. The name "Ariadne" was chosen to honor the mythical character Ariadne, daughter of Minos the king of Crete, who conceived the "Plan B" mechanism that would allow her lover to exit Daedalus' Labyrinth after killing the Minotaur.Ariadne and its informal definition as "Plan B engineering" offer surprising opportunities and properties, including not only provable operations safety with unproven components, but also a thread that can inherently be scaled up and quickly adapt to new air traffic scenarios, including the transition to free flight and accommodation of unmanned aviation. It also supports existing operations and therefore it does not conflict with current air traffic control practices. Modern computational capabilities and powerful AI algorithms make its implementation increasingly feasible to address more aspects of air traffic management.
