In an ideal world, no mistake would ever be repeated, since lessons learned from mistakes (especially those ending in tragic aviation accidents) would be immediately and permanently applied to change the safety system.
In fact, when you climb on any commercial airliner, this is a concept you trust your airline believes in to the depth of its corporate existence.
Uncovering such safety "lessons" is what the National Transportation Safety Board does. The NTSB is a mostly independent government agency that investigates all air, highway, ship, pipeline and rail accidents. It is based in Washington, D.C., and consists of more than 300 highly professional staff members. Their profession is to squeeze every ounce of useful, corrective information from every accident and not rest until all of it has been applied to make the safety system better.
In other words, the NTSB is there to make sure we don't make the same mistakes twice.
But, air safety in particular costs money. Untold barrels of money. A simple change, for instance, in the structure of an airliner that can improve the margins of safety can also cost a half million dollars per airplane. When a financially troubled airline is flying 500 or 600 such airplanes, paying for such changes is often a practical impossibility.
This is the intersection at which all the noble intentions of airline leaders and governmental regulators and NTSB investigators sometimes collide. The NTSB can recommend, but cannot order, the airlines to make changes for safety. The Federal Aviation Administration, which can issue such orders, is also required by Congress to be careful not to damage the airline industry's ability to stay solvent. And, of course, while the airlines want perfect safety, there will always be disagreements over what it takes to achieve it.
There is no clear, visible dividing line between "safe" and "unsafe." So when an airline is hemorrhaging cash, the temptation to redefine how much safety is enough becomes all but overwhelming. It's very hard for a beleaguered management team to keep from pressuring the very expensive maintenance and training functions of its airline for savings while mugging the employees for concessions and dancing around outside bankruptcy court like a child delaying a trip to the bathroom.
The good news is that for the most part -- and despite gigantic losses in the tens of billions that have in effect wiped out every dollar of profit ever earned by the airline industry -- America's airlines have done a superlative job behind the scenes of maintaining their expenditures and focus on safety. After all, the airlines invented near-perfect safety, with the FAA cheering them on, not creating the condition. (The industry has traditionally kept itself far above the FAA minimum standards, which is why we're approaching four years in the U.S. without a major airline accident).