On the thirtieth of October 1935, at an airfield in Ohio, the most advanced aircraft in the world took off, climbed a little, stalled and fell. Two of the five men on board died.
It had four engines where the aircraft it was competing against had two, and a correspondingly longer list of things to set before it could safely leave the ground.
The aeroplane was not faulty. The investigation found that a lock which holds the control surfaces still on the ground had not been released. The crew were among the most experienced pilots in the service. They knew about the lock. They simply had one more thing to remember than a person can reliably remember, and the thing they forgot was the one that mattered.
The newspapers called the machine too complicated to fly. The pilots disagreed, and their answer is why the story is still told. They did not ask for more training. They wrote a list.
It fitted on an envelope: a short set of checks for take-off, for flight, before landing, after landing. Trivial items, every one of them already known to every pilot in the room. Aircraft of that type went on to fly nearly two million miles without a comparable accident, and the pre-flight checklist became standard in aviation.
The lesson has travelled a long way from aeroplanes. When a mistake is predictable, the cure is not more skill. It is a small fixed habit, performed the same way every time, on the exact step where clever people are known to slip.