The Debrief reached out to Terry Hock, In-situ Sensing Facility (ISF) Manager at the National Center for Atmospheric Research’s Earth Observing Laboratory
In Hock’s opinion, the object most closely resembles a mylar balloon.
“There are scientific research groups that do launch balloons which they refer to as drifters,” Hock told us. “[T]his may be a possibility.”
Another possibility is that the photo depicts some variety of military radar-reflector or research balloon. However, two defense officials we spoke with said pilots who encountered the object described that, unlike a balloon under similar conditions, the object was completely motionless and seemingly unaffected by ambient air currents.
While they did not describe the photo as compelling, all three officials we spoke with seemed dismissive of the idea that it depicts a balloon. According to these sources, the photo would not have been issued if there were reasonable estimates that the object was a balloon, given the nature of the intelligence report in which it appeared.
The Debrief has not been able to speak with any of the pilots involved,
The big problem with saying it's not a balloon because it was " completely motionless and seemingly unaffected by ambient air currents" is that's exactly what a balloon looks like from the perspective of a fast-moving object.
And the other justification "the photo would not have been issued if there were reasonable estimates that the object was a balloon, given the nature of the intelligence report in which it appeared" seem circular. Once it's in some report it becomes slightly significant, then it simply remains that way because it's impossible to rule out that it might be an advanced technology craft that simply looks and moves like a balloon.
What type of balloon? Maybe just a loose partly balloon. But given the highlooking altitude, it might be something specifically designed for that, like a pico radio balloon, wich have very small payloads that might not show up in a photo.
They do use common party balloons, but seem to use partial inflation to allow them to reach higher altitudes without bursting. Sometimes using clusters
And there's a hint of a payload under the very low-resolution image of the object