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The All-domain Anomaly Resolution Office (AARO) issued this case resolution on 28 April 2025 about infrared video that a U.S. military uncrewed aerial system near Naval Air Station Sigonella recorded in December 2018 during an eruption of Mt. Etna. The operator reported a round object moving at 345 mph through the ash plume. AARO assesses with moderate confidence that the object was a balloon about one foot across, moving at about 24 mph with the wind. It found with high confidence that motion parallax caused the apparent speed and that the object never passed through the plume.
“Etna”1 page
UNCLASSIFIED 3 UNCLASSIFIED Figure 2: AARO’s top-down reconstruction of the event depicting the object’s distance from the UAS platform. (not to scale) Observable Characteristics and Attribution Size and Shape: AARO employed pixel examination to conclude with moderate confidence that the object was spherical. Its approximate diameter was 0.3 meters (1 foot). (Figure 3) Attribution: Due to the object’s size and performance characteristics, AARO assesses with moderate confidence that the object is a balloon. (UNCLASSIFIED) (UNCLASSIFIED)
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