Research news
AARO Released "UAP" Video: Mt. Etna Object
The official description, as released by the DoD: "In December 2018, a forward-looking infrared video sensor aboard an uncrewed U.S. Air Force platform captured this footage while operating over the Mediterranean Sea. This footage depicts an object that appears to be transiting a plume of superheated gas and ash produced by an eruption of Mt. Etna, a volcano in Sicily, Italy. AARO coordinated an interagency and international analytical effort that determined that optical effects from the intense atmospheric conditions near the volcano distorted the video, causing the object to appear to transit the plume. AARO assesses with moderate confidence that the footage instead depicts a balloon approximately 170 kilometers from the caldera traveling at wind speed and direction."
See more (external link) 
https://www.youtube.com/watch?v=0ODexYSBx-w