A U.S. military MQ-9 Reaper drone disappeared over the Red Sea the same day Houthi militants in Yemen claimed to have shot one down, according to a defense official with knowledge of the operation.

An MQ-9 Reaper drone crashed into the Mediterranean Sea last December after losing its propeller midflight, likely due to the failure of a ring necessary to secure the prop in place. (SrA Raya Feltner ...