The apparent Chinese spy balloon shot down off the coast of South Carolina over the weekend after it made its way across the continental U.S. was part of a larger surveillance program that the Chinese government has been conducting for “several years,” the Pentagon said Wednesday.

The announcement raises new questions about a mysterious balloon that appeared off Kauai last year that prompted U.S. fighter jets to scramble in response and comes as media reports emerge of several other apparent spy balloons making their way through U.S. airspace — including Hawaii.

Citing defense sources, Fox News reported that a suspected Chinese spy balloon crashed near Hawaii as recently as four months ago, and CNN obtained an April 2022 U.S. Air Force report titled “People’s Republic of China High-Altitude Balloon,” which found that a Chinese spy balloon had “circumnavigated the globe” in 2019 at an altitude of roughly 65,000 feet and “drifted past Hawaii and across Florida before continuing its journey.” However, CNN reported it is not clear from the documents when U.S. officials first became aware of apparent Chinese flights or what they believed their purpose was.

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Last year on Valentine’s Day, Kauai residents watched as F-22 fighter jets responded to a mysterious object in the sky off the island. Two days later Hawaii National Guard commander Maj. Gen. Kenneth Hara tweeted that U.S. Indo-Pacific Command “detected a high-altitude object floating in air in the vicinity of the Hawaiian Islands” and sent the aircraft to intercept it. Military officials described it as an “unmanned balloon without observable identification markings.”

In the following weeks, all inquiries to INDOPACOM were answered with the response: “We continue to actively monitor the object via joint capabilities. We don’t have anything else to provide at this time.” The next month Oahu residents also spotted a pair of strange balloons over Honolulu, but they were confirmed to be part of a product test by balloon company Aerostar.

The Pentagon now acknowledges four occasions during which apparent spy balloons went through U.S. territory during the administrations of Presidents Donald Trump and Joe Biden. But during a Wednesday news conference Pentagon spokesman Brig. Gen. Pat Ryder said the U.S. did not immediately identify them as Chinese surveillance balloons at the time. Ryder said “subsequent intelligence analysis” allowed the U.S. to confirm they were part of a Chinese spying effort and learn “a lot more” about the program.

However, Ryder would not provide any new details about those previous balloons and declined to say whether the balloon spotted off Kauai last year was one of the four incidents that the U.S. now acknowledges. When pressed, Ryder would only say that the balloons flew over “sites that would be of interest to the Chinese.”

Kauai is home to the U.S. Navy’s Pacific Missile Range Facility, a major weapons testing facility. Hawaii itself is the nerve center for all U.S. military operations in the region with INDOPACOM based on Oahu at Camp Smith. The Pentagon has been shifting its attention to the Pacific, which it now considers its top priority theater of operations.

John Hemmings, senior director of Honolulu think-tank Pacific Forum’s Indo-­Pacific Foreign and Security Policy Program, said that while it’s not clear what intelligence a balloon may have managed to get, “what is clear is the impact the (most recent) balloon has had on American society and on U.S.-China relations, already in deep freeze. Americans are now catching up with their government in terms of concern about the threat posed by China.”

Hemmings added that, “the fact that the surveillance balloon comes so soon after the Russian spy ship loitering off of our (Hawaiian) shores last month fortifies the impression that we are re-entering into a Cold War-like era with the authoritarian states, Russia and China.”

Carl Schuster, a retired Navy captain and instructor at Hawaii Pacific University, said that using a balloon to gather intelligence provides several advantages over satellite surveillance from space, noting that it’s close enough to easily intercept cellphone and other communication signals, among other uses.

“They can gather high-­stratosphere environmental information that may be useful for hypersonic weapon or other platform use, photographic imagery of much higher granularity, and most of all much longer overhead time,” said Schuster, “To put in another way, a duration of surveillance about 10 times that of a satellite.”

But retired Air Force Lt. Gen. Dan Leaf, who formerly served as deputy commander of U.S. forces in the Pacific at Camp Smith, said balloons also have significant disadvantages for gathering intel, noting that “they’re kind of obvious” and as was seen off the coast of South Carolina, vulnerable to attack.

But Leaf added that he “would have thought they’d be more obvious than they’ve proven to be,” and that it’s surprising to him that Chinese officials apparently felt comfortable flying the balloons in American airspace — and concerning that American officials now say they didn’t know until now.

Schuster said that it’s unclear how much American officials actually knew about these operations and why they seemingly kept quiet until now, but asserted that the silence essentially acted as an invitation for Beijing to expand its apparent operations as “the perpetrator will conclude either that you can’t detect their actions or you don’t object.”

“To suddenly react harshly to something you have ignored for one to three years creates the impression your motivation is driven by something more than the perpetrator’s actions,” said Schuster. “That doesn’t mean you take a military action, but rather issue a protest that the perpetrator’s actions are unacceptable and that you will not tolerate further incidents of that nature. As it was, our silence invited further balloon incursions and, by extension, a PRC (People’s Republic of China) miscalculation about the potential consequences of their actions.”

Military officials have confirmed that while the Air Force sent fighters to respond to the balloon off Kauai and tracked its movements for some time after, it did not shoot it down. The most recent balloon was shot down by a missile fired from an F-22 over the Atlantic on Saturday, and according to the Pentagon, the Navy and Coast Guard are still working to recover pieces for analysis.

Before Biden ordered to shoot it down, government officials debated the best course of action and publicly warned of the potential dangers should debris fall on people below while it traveled over land. Chinese officials have insisted it was a civilian balloon used for meteorological research and sharply criticized the U.S. for targeting it.

“What I think is most important to understand, and that hasn’t been fully explained, is the legal construct for interception and destruction,” said Leaf.

“There may well be a legal case for after it departs the coast but before it departs our territorial waters for downing it. But nobody’s explained that. And the reason nobody has explained … it might be that it’s ill-defined internationally” as different countries have different views of how far in the atmosphere a nation’s airspace goes — and when it stops, he said.

“What’s the boundary?” Leaf asked. “We’ve got Russian and Chinese satellites overflying us, but we don’t shoot them down. So what makes this different? And the fact that it’s kind of embarrassing, and pisses us off, shouldn’t be the rationale.”

He pointed to U.S. allegations of aggressive actions by the Chinese military in the South China Sea. Beijing claims the entire South China Sea, a critical waterway through which more than a third of all international trade travels, as its exclusive sovereign territory against the objections of neighboring countries and others whose ships and planes transit the area.

In 2016 an international court ruled in favor of the Philippines in a territorial dispute with China and declared that Beijing had “no legal basis” for its territorial claims in the South China Sea, but the Chinese military has doubled down by stationing forces on disputed reefs and islands. The U.S. military regularly deploys intelligence gathering planes and ships into the region and conducts frequent “freedom of navigation operations.” The U.S. also has been shoring up regional alliances over China’s objections.

“I don’t think the politicians on either side want to hear it, but if we’re going to demand the rule of law in other environments, we have to use it at this time … that should be the starting point for what we do,” Leaf said. “(The balloon) is a reminder of the breadth of Chinese intelligence collection, and that wherever possible we should impede or deny. But it is not — and should not be — a game changer, except that we should better define what sovereignty means with regard to our airspace.”