Norman Y. Mineta was transportation secretary in the George W. Bush administration and commerce secretary in the Clinton administration.

Last month, robbers dressed as police officers boarded a plane in Brussels and nabbed $50 million in diamonds. The break-in was a snap: The criminals cut a hole in the airport security fence and drove through it.

The ease with which anyone can penetrate an airport perimeter may shock those familiar with today’s elaborate security inside terminals. But such breaches are common in the United States and abroad. In Philadelphia last year, a driver crashed through a gate and onto a busy runway. We’ve seen similar near-catastrophes in Miami and Dallas.

If a pickup truck plows through a chain-link fence and onto a runway, the driver could be a teenager acting on a dare, an unemployed worker with a vendetta or a disturbed soul who hears voices. Or he might be a terrorist. Security officials would not immediately know, nor would it be clear whether the incident was isolated or part of a coordinated attack. Burglars aren’t the only dangerous elements with cutting tools or easy access to uniforms and forged IDs.

Perimeters are the weak link. America has the technology to monitor intruders at and even beyond an airport’s edge, but too many airports are behind the curve.

Ask whether we are doing everything possible to contain the threat, and you will hear nearly as many excuses as there are airports. Unlike terminal security, which is managed by the Transportation Security Administration (TSA), airport perimeter security is decentralized; the TSA assesses vulnerabilities, but each of the country’s 450 commercial airports budgets and manages perimeter security on its own. That’s a lot of decision-makers with differing points of view.

Budgets are tight. Airport authorities can mistakenly assume that cost increases go hand-in-hand with state-of-the-art perimeter security.

Then there’s the sheer geographic scale of the challenge. The average midsize U.S. airport covers 2,500 to 3,000 acres, with a perimeter of about 15 miles. That’s a lot of ground to cover.

These factors have barred concerted action on airport perimeter security. But those in charge need to do the math. An advanced perimeter security system is a bargain: It costs one-third the sticker price of a Boeing 737.

Forward-looking airport operators know this. Atlanta Hartsfield, Chicago O’Hare, Boston Logan and the major metropolitan New York and New Jersey airports have made measurable progress to improve perimeter security. Some use software programs that trigger perimeter-breach alarms and speed reaction times by police and emergency responders. Others have radar that can detect threats coming from “stand-off” distances, such as boats aimed at an airport perimeter.

But more need to follow their lead. Our concentrated focus on terminal security has orphaned equally important needs at the edge of airports. As Rep. Bill Keating (D-Mass.) has observed, it’s like “locking all the doors on your house but leaving the windows open.”

The United States can point with pride to the fact that not a single major airport-related terrorist event has succeeded since the terrible attacks of Sept. 11, 2001. Thanks to the creation of the TSA, broadened law enforcement powers, and the men and women on the front lines of screening, airport terminal security is at an all-time high in proficiency. Flying is safer than ever. But more than a decade after 9/11, much remains to be done.

Stopping a live threat in its tracks is the work of heroes. Airports urgently owe these brave individuals, and ourselves, the best tools available for the job.