Any American who travels must deal with the Transportation Safety Administration. The Bush administration made many mistakes in dealing with the attacks of Sept. 11, 2001. Creating a government monopoly to handle transportation safety was one of the worst.

Government’s most important duty is protecting its citizens. Still, the state need not hold a monopoly. There are police, but the Second Amendment also ensures that Americans can protect themselves.

Obviously, Uncle Sam has an interest in transportation safety. No airport or airline wants a plane hijacking. No airline (or railroad) passenger wants to die in a terrorist incident.

Unfortunately, TSA is a costly behemoth better at bureaucracy than safety. In the aftermath of the Sept. 11 killings, the Bush administration and Congress felt they had to do something, so in 2001 they created the TSA.

The following year, the agency was transferred, along with pieces of 21 other agencies, to the new Department of Homeland Security. In 2013, the TSA spent $7.9 billion and had 62,000 employees.

TSA’s main job is to protect the more than 450 commercial airports, though railways, transit systems, highways and even pipelines also are on its list. Two-thirds of the agency’s budget goes for airport screenings.

As my Cato Institute colleague Chris Edwards has documented in a new study on the agency, TSA has lived down to expectations. Noted Mr. Edwards: “TSA has often made the news for its poor performance and for abusing the civil liberties of airline passengers. It has had a troubled workforce and has made numerous dubious investments.” For all the agency’s spending and effort, “TSA’s screening performance has been no better, and possibly worse, than the performance of the remaining private screeners at U.S. airports.”

TSA has had an abundance of problems. Wasteful spending of all sorts. “Unethical and possibly illegal activities,” according to the agency inspector general. “Costly, counter-intuitive and poorly executed” operations, according to a House oversight committee. Employee misconduct. Ranking 232 out of 240 federal agencies in job satisfaction.

Worst, though, is TSA’s failure to do the job for which it was created: securing America’s airports and other transportation hubs. Reported Mr. Edwards: “There were 25,000 security breaches at U.S. airports during TSA’s first decade, despite the agency’s huge spending and all the inconveniences imposed on passengers.” In tests, the agency failed to catch as much as three-quarters of fake explosives. Expensive, high-tech machines were purchased and then abandoned.

The problem is not just operational inefficiency. The TSA doesn’t think strategically, or at least, do so effectively. Critiques of the agency range from harsh to scathing. The TSA is “too reactive and always finds itself fighting the last war.” The agency has overspent and created congestion, impeding security. Officials don’t follow “robust risk-assessment methodology.” The Department of Homeland Security “implements most of its programs with little or no evaluation of their performance.”

No planes have been hijacked since Sept. 11, 2001, but that isn’t necessarily a result of agency vigilance. Wrote Mr. Edwards: “The safety of travelers in recent years may have more to do with the dearth of terrorists in the United States and other security layers around aviation, than with the performance of TSA airport screeners.”

The alternative to the TSA monopoly is privatization. Entrust airport security to airports, which can integrate screening with other aspects of facility security and adjust to local circumstances. It’s not a leap into the unknown. “More than 80 percent of Europe’s commercial airports use private screening companies, including those in Britain, France, Germany and Spain,” wrote Mr. Edwards.

Even the 2001 legislation setting up the TSA allowed a small out for American airports. Five were allowed to go private, and 11 others have chosen to do so in the intervening 12 years. However, the Reason Foundation’s Robert Poole complained that TSA “micromanages” even private operations, “thereby making it very difficult for screening companies to innovate.” Worse, a House oversight committee charged the agency with “a history of intimidating airport operators that express an interest in” effectively firing the TSA.

Obviously, shifting security to private operators would not eliminate problems, but expanding airport flexibility and, more importantly, creating security competition, would encourage increased experimentation.

In fact, Americans started to innovate on that tragic September day a dozen years ago. When passengers on the last flight learned what their hijackers had in store, they ended the mission. Since then passengers took down the would-be shoe and underwear bombers.

Obviously, dangers remain. Paradoxically, the best way to protect people would be to abolish the TSA, limiting Washington to general oversight and tasks such as intelligence activities. Travel would be safer, security would be cheaper, and Americans would be freer.