Suppose there were 2,000 passengers -- an extraordinarily pessimistic view of the threat out there -- every day who were boarding planes at American airports with the intent to bring down the plane. That would still mean that 99.9% of passengers intended no harm to the plane or their fellow passengers.

Please quit it with the canard that airports are teeming with individuals looking to cause mass destruction. Checkpoint procedure could randomly assign half of the passengers to undergo no screening at all with no ill-effect on security.

A passenger is either a threat or they are not. You know, kind of like being a little bit pregnant.

When over 99.9% of passengers present no threat whatsoever, how can you with a straight face say that the "risk of passengers varies"?

And let's look at some of the PreCheck perks: You can leave your shoes on. So the presumption is that someone who has not had a background check is more likely to be hiding a bomb in their shoes. Yet exactly one passenger in the century-old worldwide history of aviation has tried to blow up his shoes. But yep, we can conclusively say that someone who hasn't been convicted of a crime is less likely to do so.

Risk-based security my a**.