How seriously does Washington take national security as we near the 15th anniversary of the 9/11 jihad attacks against America?

Not so much, it would appear, given that there is still no way for the government to track when or if visitors leave on their temporary visas, which was an important recommendation from the 9/11 Commission, as well as later analysis regarding the immigration enforcement aspect. If a foreigner arrives on a plane or ship, it’s essentially an open borders situation.

It’s odd the Capitol Hill denizens are so unconcerned, since they remain a major target of America’s enemies.

At least five of the Sept. 11 hijackers exploited a glaring hole in visa security to stay in the U.S. beyond their time — allowing them to board the planes and conduct their murderous attack. Fifteen years later, and despite a clear consensus on the need for improvement, that gaping hole remains.

“In too many cases that’s still happening — they come in legally, but we don’t know if they’ve left, and if they haven’t left, we don’t know where they are,” said Tom Kean, former governor of New Jersey and chairman of the 9/11 Commission that looked into the 2001 attack and crafted a long list of changes to put homeland security on firmer footing.

“That is probably the most important unfulfilled recommendation,” Mr. Kean told reporters this week ahead of the commemoration of the attack that ushered in the current war-on-terrorism era.

It’s also a key part of GOP presidential nominee Donald Trump’s immigration plan going forward.

“For years Congress has required biometric entry-exit visa tracking systems, but it has never been completed. The politicians are all talk, no action — never happens,” he last week in laying out his plans. “Hillary Clinton, all talk. Unfortunately, when there is action, it’s always the wrong decision. You ever notice? In my administration we will ensure that this system is in place. And, I will tell you, it will be on land, it will be on sea, it will be in air. We will have a proper tracking system.”

Mrs. Clinton’s presidential campaign didn’t respond to a request for comment, though, as a senator, she had positive things to say about such a system, and a year after the 2001 terrorist attacks, she even voted for legislation that required it.

But despite bipartisan support, and despite progress on many other issues identified by the 9/11 Commission, the entry-exit system remains elusive.

Overstays are one of the many areas where immigration and anti-terrorism policies overlap.

The Government Accountability Office says five of the 19 hijackers either overstayed their visas or lost their status by breaking the terms of their permits, making them illegal immigrants in the government’s eyes.

But nobody was looking for them — or even knew they’d overstayed — allowing them to blend in with millions of other illegal immigrants living and working in the U.S. at the time, carrying driver’s licenses that let them board the airplanes they’d use to kill nearly 3,000 people.

Earlier this year the Department of Homeland Security completed its first official estimate of overstays, calculating 1 percent of visitors on basic tourist or business visas — nearly 500,000 people — stayed beyond their deadlines in fiscal year 2015.

Tracking who and where they are, however, is difficult, and it’s not clear how much effort the government puts into looking for them. The administration deported just 2,500 visa overstays in 2015.

Homeland Security officials say they collect information, including fingerprints and photos, from visitors who arrive on a visa by airplane or boat. But U.S. ports aren’t set up to collect fingerprints when people leave, creating a loophole in the system that makes it difficult to be sure someone has left the way he came.

And land borders are another issue altogether. While officers at the U.S.-Canada border do name checks and share the information with each other, they don’t collect fingerprints. And the U.S. lacks a similar agreement with Mexico, meaning there aren’t even any name checks for the millions who cross the southwest border.

U.S. Customs and Border Protection is trying a few solutions. CBP is running a pilot program at 10 airports, testing mobile fingerprint-collection devices on select flights, and from December through May, it did name checks and fingerprint collection at the Otay Mesa land port in California.

Homeland Security Secretary Jeh Johnson has set a 2018 deadline for collecting biometrics from departing passengers at the country’s top airports.

“We will have this deployed and operational by fall of 2018. The secretary’s committed to 2018 to be doing this, and we intend to do this,” John Wagner, deputy assistant commissioner at CBP, assured Congress earlier this year.

Mr. Kean and fellow 9/11 Commission leader Lee Hamilton, a former congressman, will be watching.

They said they are putting together a panel under the auspices of the Bipartisan Policy Center aimed at revisiting the war on terror and assessing whether the U.S. is safer.

The two men said that the country has escaped a large-scale attack, but has seen its share of the small attacks that have spread across the globe in the last 15 years.

They said Congress needs to do a better job of oversight, the administration needs to hone its goals, and the U.S. needs to pay more attention to the ideological battle against radical forces.

“We need a lot of help here, but we’ve got to crank it up — do better what we’re doing and do some things we haven’t been doing,” Mr. Hamilton said.

He also dismissed fears over refugees from terrorist-connected countries, saying U.S. screening works “pretty well,” and added that in order to fight the ideological battle, the American government must do its fair share.

“If you look at what the European countries have done, our effort looks fairly meager. I would be on the side of those that think we should do more,” he said.