The United States is on the verge of leaving a decades-old treaty that has helped it gain intelligence on the militaries of potential foes, especially Russia. If the Trump administration goes through with the decision, the US will lose a valuable intelligence-gathering method and potentially make the world less safe.

According to multiple reports, the White House wants to pull the US out of the Open Skies Treaty, one of the most wide-ranging arms control pacts in the world. Originally an idea by President Dwight Eisenhower and made reality by President George H.W. Bush in 1992, it allows nations to conduct unarmed flights over another country’s military installations and other areas of concern.

Put into effect 10 years later, it has since helped the 34 North American and European signatories — including the US and Russia — gain confidence that others weren’t developing advanced weapons in secret or planning big attacks.

In other words, the treaty was put into place to prevent arms races — and even wars. “If the United States abandons this agreement, the result will likely be the collapse all that is left of conventional arms control in Europe,” says Alexandra Bell, an expert at the Center for Arms Control and Non-Proliferation.

Here’s why she and others say this: The Open Skies Treaty includes 32 other countries but it’s really all about the US and Russia. The countries have nuclear arsenals and militaries that dwarf any in the accord and staying in it allows both to gain critical information on each other. What’s more, the imagery they collect is shared among all the signatories, giving some less technologically advanced nations their only source of overhead intelligence. That’s important for, say, Ukraine, a treaty member that wants to know about Russian military movements on its border.

But should the US leave the deal, Russia will likely bow out, too. That would mean in one fell swoop Washington would lose an important way to keep tabs on Moscow’s weapons development, worsen already bad relations with the Kremlin, and take away a vital intelligence tool from American allies.

“Withdrawal risks dividing the transatlantic alliance and would further undermine America’s reliability as a stable and predictable partner when it comes to European security,” Rep. Eliot Engel, the House Foreign Affairs Committee chair, wrote in a letter to National Security Adviser Robert O’Brien this week. “[I] strongly urge you against such a reckless action.”

How the Open Skies Treaty works

To understand why arms-control advocates are so passionate about the Open Skies Treaty, you first need to understand what it actually does.

A country that has signed onto the treaty must give another treaty-bound nation at least 72-hours notice that it plans to conduct an overflight, and each country must accept a certain quota of overflights based on how geographically big it is.

So, if the Russian Air Force wanted to fly above the most sensitive US military installations, it would give its American counterparts that advance notice. Then, 24 hours before the overflights are to begin, Russia would have to give the US its flight plan so the plane can be tracked accordingly.

This isn’t just a hypothetical procedure. It’s been put into effect numerous times.

In April, for example, a Russian Air Force jet spent four days flying around the US, even passing above Area 51 and other secretive locations. And the US military also gets to fly above Russian territory, using two aging Boeing aircraft based out of Nebraska. In fact, as of 2016, the US flew over Russia around 200 times and Russia flew over the US about 70 times — meaning the deal has been better for Washington than Moscow.

The aircraft can have four types of sensors on them: optical panoramic and framing cameras, video cameras with real-time display, infra-red line-scanning devices, and sideways-looking synthetic aperture radar. This allows the planes to get up-to-the-minute information with minimal weather problems and target precisely what they want to see, when they want to see it.

And yet, it seems having near unimpeded access to fly over Russia doesn’t suit the Trump administration.

Why the Trump administration might want out of the Open Skies Treaty

Those who rail against the treaty — including the administration, it seems — make three main arguments against it.

First, as Sen. Tom Cotton (R-AR) articulated on Tuesday, the US could spend its money elsewhere. After all, the US has many spy satellites in space so the utility of spending money to fly creaking planes for days over Russian and other territory doesn’t make much sense, the treaty’s critics say. The fiscal year 2019 defense appropriations had $146 million earmarked to begin buying new equipment for the program.

The president should withdraw from the Open Skies treaty and redeploy the hundreds of millions of dollars the Pentagon wastes on the flights and equipment to increase U.S. combat power. pic.twitter.com/YYewKwessO — Tom Cotton (@SenTomCotton) October 8, 2019

Second, many say Russia is cheating as a treaty member. For example, Russia restricted US overflights of Kaliningrad — the Russian exclave in Europe’s northeast — to 310 miles in the territory and within a six-mile corridor of its border with Georgian conflict zones Abkhazia and South Ossetia. Meanwhile, the US rarely if ever impedes Russia from at least attempting to see what it wants.

That wasn’t much of a concern for former Secretary of Defense James Mattis, though. He told Sen. Deb Fischer (R-NE) in a May 2018 letter that “it is in our Nation’s best interest to remain a party to the Open Skies Treaty” after she complained about Russia’s cheating.

Many experts side with Mattis. “These issues do not rise to the level of a material breach, nor do they justify withdrawal,” Kingston Reif, an expert at the Arms Control Association, told me.

Third, some experts claim the deal helps Russia much more than it helps America. “I’m supportive of leaving” the treaty, Rebeccah Heinrichs, a nuclear expert at the Hudson Institute, told me. “It’s critical to Russia’s intelligence operation which it exploits to our disadvantage. They need it more than we do.”

“Between the technology they use, what they’re looking at, and how they have denied certain overflights over parts of their territory, it does force us to consider that maybe we’re enabling them even as they seek to undermine us,” she continued.

This is a concern some top military officials have had, as well. In 2016, then-Defense Intelligence Agency Director Gen. Vincent Stewart told the House Armed Services Committee that he was worried about what Russia could learn thanks to the treaty.

“The things that you can see, the amount of data you can collect, the things you can do with post-processing, allows Russia, in my opinion, to get incredible foundational intelligence on critical infrastructure, bases, ports, all of our facilities,” he said. “So from my perspective, it gives them a significant advantage.” He later added that he’d “love to deny” Russia allowed overflights.

That’s all fair, especially if Russia is getting better quality information than the US is. But advocates of the treaty note that what Moscow learns is outweighed by what the US obtains and can share with its allies in the accord, particularly Ukraine. “The treaty has been of particular value recently in countering Russian disinformation and aggression against Ukraine,” says Reif.

There is major concern that the Trump administration simply wants out of arms-control treaties in general and with Russia in particular. Trump withdrew the US from the UN Arms Trade Treaty, an international arms sals agreement, and ended the Intermediate Nuclear Forces Treaty with Russia that banned ground-based, medium-range nuclear missiles.

Advocates for these and other agreements say the US is leaving treaties that, while imperfect, give Russia more authority to build advanced weapons while lowering trust between the world’s foremost nuclear powers.

That, among other reasons, is why so many experts are upset that the Trump administration may leave Open Skies in the coming days: because the US could lose more than it gains. “The United States gains nothing from leaving the treaty,” Bell told me.

Update, October 10, 2019: This article originally called the overflights “spy flights.” We’ve changed it now to “observation flights” to more appropriately describe the matter.