I have seven HBAL targets HBAL532 N259th, HBAL534 N254th, etc flying down around Wilmington NC. It seems they belong to Loon internet services. The website says they are shutting down. They also seem to have tie in to Alphabet (Google)
I saw them, too. I’m near Hillsborough, NC.
I heard it was a Google project they were trying to pass on, but no one wants to take them on, due to the cost of maintenance etc.
I see HBAL527 flew over Montana and is currently close to Casper WY at about 55,000 ft. Hadn’t seen balloons before.
Maybe they have to be over a certain location before they drop them. So they wait and let them drift?