The Dirty Dozen: 12 common causes of mistakes in the aviation workplace

During the late 1980s and early 1990s, there were a spate of maintenance related aviation incidents in Canada. These incidents spurred Transport Canada to launch an initiative that would aid aviation companies in their fight to prevent unnecessary accidents.

A maintenance engineer changing the front wheels of an aircraft.

A maintenance engineer changing the front wheels of an aircraft.


Gordon Dupont, who was a Special Program Coordinator at Transport Canada at the time, is credited with the introduction of “The Dirty Dozen” which was the identification of 12 human factor elements highly likely to “degrade people’s ability to perform effectively and safely, leading to maintenance errors”.

The Dirty Dozen consists of 12 identified human factors. They are:

Lack of Communication: The lack of clear direct statements and good, active listening skills.

Complacency: Self-satisfaction accompanied by loss of awareness of the potential dangers.

Lack of Knowledge: Lack of experience or training in the task at hand.

Distraction: Drawing one’s attention away from a task.

Lack of teamwork: Lack of working together to achieve a common goal.

Fatigue: Weariness from labor or exertion, nervous exhaustion or the temporary loss of power to respond.

Lack of Resources: Failure to use or acquire the appropriate tools, equipment, information and procedures for the task at hand.

Pressure: Pushing for something in spite of opposing odds, creating a sense of urgency or hassle.

Lack of Assertiveness: A lack of positive communication of one’s ideas, wants and needs.

Stress: Mental, emotional or physical tension, strain or distress.

Lack of Awareness: Failure to be alert or vigilant in observing.

Norms: Commonly accepted practices where assumptions are made that the course of action or procedure is correct based on history without re- validating or verifying the current procedures.

Since 1993 all areas of the aviation industry, not just aircraft maintenance, have found the Dirty Dozen a useful introduction to open discussions into human error in their businesses, organizations and workplaces. So, it may be possible to find Dirty Dozen lists for pilots, ramp workers, air traffic controllers and cabin crew.

Updated: January 9, 2016 — 17:18

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