Someone broke into a cargo hatch of the Il-80 Maxdome, Russia’s “Doomsday plane,” and stole radio equipment, Russian media report.

The incident occurred as the plane was undergoing maintenance at Taganrog-Yuzhny airfield, Rostov region, Russia.

The aircraft involved in the incident is one of the four Il-80 aircraft, heavily modified Il-86 airliners used as airborne command center in a role similar to that of the U.S. Boeing E-4B since the mid-1980s.

The investigation revealed that 39 radio stations were missing from the plane. The facility’s employees could be the ones involved in the brazen theft, the report reads.

One version of the reason behind the theft is espionage as the aircraft contained “sensitive” equipment. Another version says the thieves could want special parts, especially those containing rare metals.