In Serious Play, Michael Schrage describes how a life-or-death management issue was uncovered by accident, when regulators went to test the safety of pilots working longer shifts in the newly deregulated air-travel market of the 1980s:
The researchers tested two groups of test crews: those who flew the scenario after a minimum of two days off, as if it were the first leg of a three-day trip (preduty) and those who flew the scenario as the last segment of a three-day trip (postduty). The scenario was characterized by poor weather that forced a missed approach to a landing. The missed approach was further complicated by a hydraulic-system failure that created a high-speed, high-workload situation. The two pilots had to select an alternate landing site and manually extend the plane’s gears and flaps while flying an approach at higher-than-normal speed.
As expected, the postduty crews had had less presimulation sleep and reported singificantly more fatigue. But, to the researcher’ astonishment, “fatigued crews were rated as performing significatnly better and made fewer serious operational errors than the rested, preduty crews.”
As NASA’s researchers commented, “in hindsight, the finding shouldn’t have been a surprise at all. By the very nature of the scheduling, most crews in the postduty condition had just completed three days of operation as a team. By contrast, those in the preduty condition normally did not have the beneft of recent experience with their other crew members.”
When the researchers reanalyzed their data, fatigue was found to be a far less statistically significant safety factor than whether the crews had recently flown together. The simulation fidings indicate that crew schedules resulting in frequent mixing of pilot teams can have significant operational implications. The NASA researchers noted that no fewer than three of the wors 1980s-era accidents — a stall under icy conditions, an aborted takeoff that landed the plane in the water, and a runway collison in dense fog — all involved crews paired for the first time.