Updated at 8:37 a.m. EDT

It is not every day that an American airport issues a ground stop due to a Chinese spy balloon hovering overhead, but that appears to be the reason why the FAA closed airspace for two hours over the airport at Billings, Montana, on Wednesday. Air traffic has since resumed. 

The Billings Gazette reported on Thursday that the ground stop covered a 50-mile radius that included the Billings airport and was announced through the Automatic Terminal Information Service, a broadcast system used to communicate vital information to pilots, airports, and air traffic controllers.

On Thursday the Pentagon announced that it was tracking a Chinese spy balloon flying at a high altitude over American territory, passing over sensitive military installations. According to various press and eyewitness reports, the length of the large white balloon approximated that of three school buses. An anonymous defense official told the AP that commercial pilots could spot the immense spy balloon from their cockpit

When he was informed of the intrusion, President Biden reportedly asked Secretary Austin to present him with the best options. 

A senior defense official said that America scrambled fighter jets, including F-22s, to shoot down the balloon if ordered, but that the decision was made not to shoot because of the potential danger to people on the ground from the debris, a senior defense department official told reporters. Mr. Austin and the chairman of the Joint Chiefs of Staff, General Milley, advised against taking “kinetic action.”

“We have very high confidence that the balloon belongs to China,” the senior defense official told reporters. It is an open question whether bringing the balloon down would have posed a danger on the ground in sparsely populated Montana. 

An electronics engineer and colonel in the Hellenic Air Force, Konstantinos Zikidis, told the Sun, “In case of falling debris, it would not go unnoticed; however no significant harm should be expected.”

A Pentagon spokesman, Patrick Ryder, said that the America-Canada Aerospace Defense Command, known as Norad, is closely monitoring the balloon’s continued trajectory, which could now be over Canadian airspace. 

“China’s brazen disregard for U.S. sovereignty is a destabilizing action that must be addressed, and President Biden cannot be silent,” Speaker McCarthy said via Twitter. Mr. McCarthy added, “I am requesting a Gang of Eight briefing.”  The Gang of Eight is the congressional leaders who are briefed on classified intelligence matters by the executive branch.

A retired Air Force colonel, Cedric Leighton, told CNN that China “could be scooping up signals intelligence, looking at our cellphone and radio traffic, and looking at our government’s command-and-control networks.” America “has ballistic missile silos in Montana, North Dakota, and Wyoming,” Mr. Leighton said, “and these are the kind of things they could be looking at, as well as the strategic bomber bases that we have in the Dakotas.”

A senior Pentagon official corroborated that assessment, telling reporters, “Clearly the balloon is for intelligence gathering and its current course takes it over sensitive locations,” notably air bases and nuclear missile silos, some of which are in Montana. The northern state  houses Malmstrom Air Force Base, one of America’s three nuclear missile silo fields.

While the balloon entered American airspace an unspecified number of days ago, American intelligence had reportedly put it under surveillance long before that. This is apparently the first time a Chinese balloon has lingered over American airspace for this long. 

Washington raised the issue with Beijing. “We addressed the seriousness of the incident,” the official said, adding: “We told them clearly that we will do whatever is necessary to protect our people and our territory.”

A spokesman for Communist China’s foreign ministry, Mao Ning, told reporters that “China is a responsible country and has always strictly abided by international laws, and China has no intention of violating the territory and airspace of any sovereign country.” Mr. Ning added that “as for the balloon, we are looking into and verifying the situation and hope that both sides can handle this together calmly and carefully.”

The incident comes just ahead of a rare visit to Beijing by Secretary Blinken, and at a time when tensions between Washington and Beijing over a host of issues are — literally, it now appears — soaring.

In a letter to Mr. Austin, Senator Daines, a Republican of Montana, said that “the fact that this balloon was occupying Montana airspace creates significant concern that Malmstrom Air Force Base and the United State’s intercontinental ballistic missile fields are the targets of this intelligence gathering mission.”

The senator’s letter, sent on Thursday, referred to the incident in the past tense, to wit: ”It is vital to establish the flight path of this balloon, any compromised U.S. national security assets, and all telecom or IT infrastructure on the ground within the U.S. that this spy balloon was utilizing.”

As of Friday morning, though, the exact whereabouts of the Chinese balloon were not publicly known.