Definition
A state of self-satisfied confidence in one's own competence that leads to reduced vigilance, skipped procedures, and inattention to potential hazards.
Plain English
Feeling so comfortable with a task that you stop paying full attention to it. In flying, this often shows up as 'I've done this a hundred times, I don't need the checklist.'
Context Anchor
Seen in checklist use, cockpit discipline, and safety discussions about routine tasks that still require full attention.
Derivation
From the Latin complacere, meaning 'to be very pleasing.' Originally it described a pleasant, contented feeling. Over time the meaning shifted to describe being so pleased with oneself that one stops trying — which is exactly the trap pilots fall into when familiarity replaces discipline.
Why Pilots Care
Complacency is a leading contributor to checklist omissions and procedural errors even among experienced pilots.
Analogy
Like driving home on autopilot and missing your exit because the route feels too familiar to need active thought.
Intuition Check
Complacent does not just mean calm or confident. It means too unworried to give the task the attention it still needs.
Example Sentence 1
After a thousand hours in the same airplane, the pilot grew complacent and began running the before-takeoff checks from memory, eventually missing a flap setting.
Example Sentence 2
To avoid becoming complacent, pilots are trained to treat every checklist as if it were the first time they have seen it.