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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 1 UNCLASSIFIED All-domain Anomaly Resolution Office U.S. Department of Defense Case: “Mt. Etna Object” Case Resolution | 28 April 2025 Case Synopsis Location: Mt. Etna, Italy Date: December 2018 Object Altitude (reported): 500 feet Object Altitude (assessed): 15,000 feet Object Speed (reported): 345 mph Object Speed (assessed): 24 mph Object Shape (reported): Round Object Shape (assessed): Spherical Reporter: U.S. Military UAS operators Data Type: Infrared Reported Behavior: An object moving at high speeds through Mt. Etna’s ash plume. Assessed Behavior: The object did not demonstrate anomalous performance characteristics. Confidence: Moderate confidence the object was a balloon. High confidence the object did not demonstrate anomalous performance characteristics. AARO Assessment and Case Status AARO assesses with moderate confidence that the object was a balloon. AARO assesses with high confidence that the object did not exhibit anomalous behavior. Case Overview In December 2018, a shortwave infrared (SWIR) camera onboard a U.S. military uncrewed aerial system (UAS) operating near U.S. Naval Air Station Sigonella over the Mediterranean Sea south of Sicily, Italy, captured 12 minutes of infrared video of an eruption of Mt. Etna. For approximately four and a half minutes, a round object appears on the video and seems to exhibit anomalous performance characteristics by moving at high speeds and transiting a superheated gas and ash plume produced by the eruption. The UAS operator reported that the object’s flight behavior was seemingly unaffected by transiting the plume, with no discernable impact on its performance, altitude, or bearing. The operator reported the object’s speed as approximately 555 kph (345 mph). Key Findings AARO assesses with high confidence that: • Optical effects, turbulent atmospheric conditions, and limitations in sensor capability distorted the object’s apparent behavior, leading to an inaccurate initial assessment of its performance characteristics. 25-P-0694
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