The militaries of South Korea and the U.S. flew multiple surveillance flights over the Korean Peninsula in recent days to strengthen their monitoring of the North.
Aviation tracker 'No Callsign' tweeted that a U.S. spy plane, the RC-12-X Guardrail surveillance aircraft, was spotted this morning.
A day earlier, six of the same type of planes were seen operating along with a U.S. Air Force RC-135-W Rivet Joint.
Also spotted over the Peninsula on Monday was a South Korean Air Force AWACS (a-wax) aircraft the E-737 Peace Eye.
It's rare for eight of the allies' spy planes to be operating on the same day.