There are good checklists and bad, Boorman explained. Bad checklists are vague and imprecise. They are too long; they are hard to use; they are impractical. They are made by desk jockeys with no awareness of the situations in which they are to be deployed. They treat the people using the tools as dumb and try to spell out every single step. They turn people's brains off rather than turn them on.

Good checklists, on the other hand, are precise. They are efficient, to the point, and easy to use even in the most difficult situations. They do not try to spell out everything - a checklist cannot fly a plane. Instead, they provide reminders of only the most critical and important steps - the ones that even the highly skilled professionals using them could miss.

Good checklists are, above all, practical. The power of checklists is limited, Boorman emphasized. They can help experts remember how to manage a complex process or configure a complex machine. They can make priorities clearer and prompt people to function better as a team. By themselves, however, checklists cannot make anyone follow them.

Pilots nonetheless turn to their checklists for two reasons. First, they are trained to do so. They learn from the beginning of flight school that their memory and judgment are unreliable and that lives depend on their recognizing that fact. Second, the checklists have proved their worth - they work. However much pilots are taught to trust their procedures more than their instincts, that doesn't mean they will do so blindly.

Aviation checklists are by no means perfect. Some have been found confusing or unclear or flawed. Nonetheless, they have earned pilots' faith. Face-to-face with catastrophe, they are astonishingly willing to turn to their checklists.