The U.S. military reportedly flew a surveillance plane over the Korean Peninsula on Monday, two days before North Korean leader Kim Jong-un's birthday.

According to private aviation tracker Aircraft Spots, a U.S. Air Force RC-135W Rivet Joint flew some nine-point-four kilometers over South Korea at an undisclosed time.

The same type of plane, which is used to detect signals prior to a missile launch, was spotted over the peninsula on December 30, 31 and January first as well.

U.S. media reports suggested earlier that the Pentagon sees a possibility that North Korea may engage in a provocation on or around Kim's birthday on January eighth or the birthday of his late father Kim Jong-il on February 16.