The chance of dying in an airplane is vanishingly small. The chance of being killed by a terrorist in an airplane is smaller still. Mark Stewart, a civil engineer who studies probabilistic risk, has put the odds at one in 90 million a year. Looking at these figures dispassionately, one might wonder if the Transportation Security Administration has found the right balance between safety and convenience with its notoriously burdensome airport screening procedures.

The T.S.A. seems to understand that the status quo is barely tolerable for many travelers and is seeking to reduce the hassle. It recently announced that it was extending eligibility for a prescreening program called PreCheck to all American citizens. People can apply online before visiting an enrollment site in person, providing their fingerprints, passing a background check and paying $85 for a five-year term. In exchange, they will gain access to a special lane at the airport where they can keep their belts buckled, their shoes tied and their liquids in their carry-on bags (but still no more than 3.4 ounces, please).

PreCheck will provide a measure of relief for anyone who signs on. But it is absurd for the T.S.A. to demand background checks and fingerprinting for what amount to small modifications in the screening routine. The agency could relax airport security for everyone without gravely endangering the traveling public.

The former head of the T.S.A., Kip Hawley, has argued that the agency should allow passengers to carry on all liquids, in any quantity. As a safeguard against explosives, passengers would simply have to put their liters of Evian in gray bins and pass them through scanners. Mr. Hawley sees reasons for keeping footwear checks, but those, too, are of questionable value. Passengers do not remove their shoes in the European Union, or even in Israel, one of the world’s most security-conscious countries, with a famously stringent screening process.