WASHINGTON >> Wafting across the United States and into the attention of an alarmed national and global public, a giant Chinese balloon has changed Americans’ awareness of all the stuff floating in the air and how defense officials watch for it and respond.

President Joe Biden said Thursday that the U.S. is updating its guidelines for monitoring and reacting to unknown aerial objects. That’s after the discovery of a suspected Chinese spy balloon transiting the country triggered high-stakes drama, including the U.S. shootdowns of that balloon, and three smaller ones days later.

Biden said officials suspect the three subsequent balloons were ordinary ones. That could mean ones used for research, weather, recreational or commercial purposes. Officials have been unable to recover any of the remains of those three balloons, and late Friday the U.S. military announced it had ended the search for the objects that were shot down near Deadhorse, Alaska, and over Lake Huron on Feb. 10 and 12.

In all, the episodes opened the eyes of the public to two realities.

One: China is operating a military-linked aerial surveillance program that has targeted more than 40 countries, according to the Biden administration. China denies it.

Two: There’s a whole lot of other junk floating up there, too.

A look at why there are so many balloons up there — launched for purposes of war, weather, science, business or just goofing around; why they’re getting attention now; and how the U.S. is likely to watch for and respond to slow-moving flying objects going forward.

WHAT ARE ALL THOSE BALLOONS DOING UP THERE?

Some are up there for spying or fighting. Humans have hooked bombs to balloons since at least the 1840s, when winds blew some of the balloon-borne bombs launched against Venice back on the Austrian launchers. In the U.S. Civil War, Union and Confederate soldiers floated up over front lines in balloons to assess enemy positions and direct fire.

And when it comes to peacetime uses, the cheapness of balloons makes them a favorite aerial platform for all kinds of uses, serious and idle. That includes everything down to “college fraternities with nothing better to do and $10,000,” joked Rep. Jim Himes of Connecticut, the ranking Democrat on the House Intelligence Committee.

Himes’ role on the committee involved him in a congressionally mandated intelligence and military review of the most credible of sightings of unidentified aerial phenomena, or UFOs. That review also drove home to him and other lawmakers “how much stuff there is floating around, in particular balloons,” Himes said.

For the National Weather Service, balloons are the main means of above-ground forecasting. Forecasters launch balloons twice daily from nearly 900 locations around the world, including nearly 100 in the United States.

High-altitude balloons also help scientists peer out into space from near the edges of the Earth’s atmosphere. NASA runs a national balloon program office, helping coordinate launches from east Texas and other sites for universities, foreign groups and other research programs. School science classes launch balloons, wildlife watchers launch balloons.

Commercial interests also send balloons up — such as Google’s effort to provide internet service via giant balloons.

And $12 gets hobby balloonists — who use balloons for ham radio or just for the pleasure of launching and tracking — balloons capable of getting up to 40,000 feet and higher.

That’s roughly around the altitude that the U.S. military says the three smaller balloons were at when U.S. missiles ended their flights.

Most pilots probably wouldn’t even be aware of a collision with such a balloon, said Ron Meadows, who produces balloons — with transmitters the size of a popsicle stick — for middle schools and universities to use for science education.

All it “does is report its location and speed,” Meadows said. “It’s not a threat to anyone.”

Among hobby balloonists, there are suspicions that a balloon declared missing by the Northern Illinois Bottlecap Brigade was one of the ones shot down, as the publication Aviation Week Network first reported. White House National Security Council spokesman John Kirby said Friday the administration was not able to confirm those reports

And it’s not just the United States’ Mylar, foil and plastic overhead. Wind patterns known as the Westerlies sweep airborne things ranging from Beijing’s tailpipe soot and the charred chunks of Siberian forest fires swinging over the Arctic and into the United States. China says its big balloon was a meteorological and research one that got picked up by the Westerlies. The U.S. says the balloon was at least partly maneuverable.

WHY ARE WE JUST NOW SPOTTING ALL THESE BALLOONS?

Short answer: Because we are just now looking for them.

Balloons’ rise to global prominence got a lift starting in the past few years. Congress directed the Director of National Intelligence to pull together everything the government has learned about unidentified aerial phenomena. That included creating a Defense Department UAP task force.

Last year, in the first congressional hearing on unidentified airborne objects in a half-century, Scott W. Bray, the deputy director of Naval intelligence, told lawmakers that improved sensors, an increase in drones and other non-military unmanned aerial systems, and yes, “aerial clutter” including random balloons were leading to people noticing more unidentified airborne objects.

That awareness kicked into overdrive this month, after the U.S. military and then the U.S. public spotted the Chinese balloon floating down from the High North. While the U.S. says previous Chinese balloons have entered U.S. territory, this was the first one of them to slowly cross the United States in plain view of the public.

That balloon, and what had been growing official awareness of a Chinese military-linked balloon surveillance campaign that had targeted dozens of countries, led U.S. officials to change radar and other sensor settings, screening more closely for slow-moving objects in the air as well as fast ones.

SIDEWINDER MISSILES: A LONG-TERM BALLOON STRATEGY?

Post big Chinese balloon, U.S. defense officials are expected to keep up broader monitoring so that balloons remain on the radar, but fine-tune the response.

Biden’s order to the Air Force to shoot down the three smaller airborne objects with Sidewinder missiles left him fending off Republican accusations he was too trigger-happy. Biden says all four shootdowns were warranted since the balloons could have posed dangers to civilian aircraft. Hobby balloons with payloads of only a few pounds are not covered by many FAA airspace rules.

Biden says the U.S. is developing “sharper rules” to track, monitor and potentially shoot down unknown aerial objects.

He directed national security adviser Jake Sullivan to lead an interagency team to review the procedures.

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Todd Richmond in Madison, Wisconsin, and Chris Megerian in Washington contributed.