Vigilance impossible: Diligence, distraction, and daydreaming all lead to failures in a practical monitoring task.

•We studied monitoring performance among airline pilots in a high-fidelity simulator.•Unlike in laboratory studies, monitoring did not deteriorate across prolonged vigils.•Monitoring was often interrupted by other pop-up tasks and monitoring lapses ensued.•But when free to monitor, pilots often mind wandered which also led to lapses.•Diligence, distraction, and daydreaming all seem to lead to monitoring lapses.