A Boeing E-6B Mercury operated by the U.S. Navy, one of the service’s airborne nuclear command posts commonly known as the “Doomsday plane,” disappeared from civilian flight-tracking platforms Friday morning while operating over the Atlantic Ocean, according to tracking data, the Daily Mail reports.

The aircraft, using callsign AFD FE2, was last observed on ADS-B Exchange and similar services around 8:30 a.m. EST approximately 60 miles east of Virginia Beach, Virginia. The plane had departed Naval Air Station Patuxent River, Maryland, on a standard southeast track over Chesapeake Bay before its transponder was deactivated.

During TACAMO (Take Charge and Move Out) missions, the E-6B typically enters restricted warning areas, deploys a miles-long trailing-wire antenna, and flies extended racetrack patterns to relay secure communications to U.S. ballistic-missile submarines and other strategic assets, Key Aero reports.

The E-6B fleet also performs the Airborne National Command Post “Looking Glass” mission, equipped with the Airborne Launch Control System (ALCS) capable of transmitting launch orders to silo-based intercontinental ballistic missiles if ground command centers are destroyed. An E-6B conducted an ALCS simulated ICBM launch exercise as recently as April.

The Navy and U.S. Strategic Command have not commented on Friday’s flight.

In August, another E-6B was recently forward-deployed to Pituffik Space Base in northern Greenland for what the service claimed was routine operations, including exercises with nuclear submarines in both the Atlantic and Pacific. However, aviation analysts, including Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, described the E-6B aircraft's flight near Greenland as unusual. Historical E-6B forward operating locations have included Guam, Norway, Germany, Spain, and the U.K., according to Newsweek.

“Naval Strategic Forces conduct global operations in coordination with combatant commands, services, and allies and partner nations, even in the High North,” Commander Jason Fischer, a spokesman for U.S. Submarine Forces, told Newsweek.