Trajectory-based complexity (TBX): A modified aircraft count to predict sector complexity during trajectory-based operations

• Aircraft count insufficient to predict controller workload under all conditions • TBX uses a simple framework to adjust the aircraft count according to variations of tractable and predictable primary and secondary complexity factors. • TBX factors were derived from air traffic personnel's inputs. The factors were easy to understand and easy to act upon. • TBX was successfully used in multiple HITLs and provides promise to be a good additional metrics to aircraft count