May 1 (UPI) -- The U.S. military deployed supersonic bombers in the Pacific and surveillance aircraft over the Korean Peninsula, as speculation continues over the status of Kim Jong Un.
Online aviation tracker Aircraft Spot published data of the movements of the movements of the RC-135W, or Rivet Joint, on Friday.
"USAF RC-135W 62-4139 LEVET22 operating over South Korea," the tracker tweeted.
The spy plane was deployed to South Korean airspace and flew near the Seoul metropolitan area and over the cities of Incheon and Gyeonggi Province's Gwangju city, according to Yonhap news agency.
The Rivet Joint is designed to gather telemetry and other electronic intelligence data before missile launches. It has been detected in South Korean airspace in recent months.
In a separate tweet, Aircraft Spot confirmed two supersonic bombers, the U.S. Air Force's B-1B Lancers, flew from the U.S. mainland to the East China Sea near Okinawa, then to Andersen Air Force Base in Guam.
The supersonic bombers have been active in the Pacific. On Thursday, the U.S. Indo-Pacific Command confirmed two B-1Bs carried out a 32-hour flight over the South China Sea from Ellsworth Air Force Base in South Dakota.
"This operation demonstrates the U.S. Air Force's dynamic force employment model in line with the National Defense Strategy's objectives of strategic predictability with persistent bomber presence, assuring allies and partners," the U.S. military said.
Before Kim went missing for 20 days, North Korea had warned the United States of consequences if its demands for sanctions relief were not met.
Kim had also vowed to introduce a "new strategic weapon," raising concerns in South Korea earlier this year the regime could be pursuing the development of multiple independently targetable re-entry vehicles.
The South Korean government has said they have detected no unusual movements following unconfirmed reports of Kim's health.