The official description
AARO assesses that this video, whose uploader-defined title is, “09JUN2021 [Platform] observed UAP in the ECS,” is likely derived from an infrared sensor aboard a U.S. military platform operating above the East China Sea in 2021. A user uploaded this video to a classified network in June 2021. Video Duration: 00:00:23 Video Description: 00:01-00:18: The sensor pans to track an area of contrast. At the 18 second mark, the sensor loses sight of the object. 00:19-00:23: No content.
Quoted from the U.S. Department of War, PURSUE UAP releases. Read every file for this incident in Official files or at war.gov/UFO.