Adam Grant on how to identify and develop high-potential leaders

I agree with you, people have to have "Ability X," whatever that particular ability happens to be or they cannot improve upon it.
To this point, I have trained many Air Traffic Controllers, some from the very start, many from already having certification to improve their skill. I have also eliminated 5 people from the career field all for the same reason, they could not make a decision in a timely manner.

Everyone I trained I told them I can teach you to make the right decision, but you have to make the decision on your own. I cannot train your mind to make a decision.

In that job you have to make many split second decisions, some as simple as to who to talk to first. Some that have a ripple effect that if you change Aircraft A's movement in some way it will effect Aircraft B, C, D, and down the line.