“”the military’s ability to respond to balloons and similar craft is constrained by physics and the capabilities of current weapons,” The Washington Post reports, and you can’t really pop a giant balloon with gunfire at 40,000 feet.
“You can fill a balloon full of bullet holes, and it’s going to stay at altitude,” David Deptula, a retired Air Force lieutenant general and fighter pilot, tells the Post. The air pressure that high up doesn’t allow helium to freely escape through small holes, even if fighter jets flying by at hundreds of miles per hour can riddle the near-stationary balloon with bullets.”
https://www.yahoo.com/news/why-u-used-missiles-not-125447249.html