The aircraft of European Commission President Ursula von der Leyen lost access to GPS navigation services while approaching Plovdiv airport in Bulgaria on Sunday, with pilots forced to land using traditional paper charts as the aircraft lost all electronic navigation systems.

According to three officials who spoke to the Financial Times, the incident is being treated as a sabotage operation by Russia. “The entire area around the airport lost GPS. It was undeniable interference,” one of the officials said.

The plane circled for nearly an hour before the pilot decided to land manually using analog maps. The official described the interruption as “undeniable interference.”

The von der Leyen pilot was forced to wait in the air for about an hour before deciding to make the landing using printed charts.

The signal disruption may have been caused by jamming or spoofing that completely disabled satellite navigation systems in the area.

The outage is associated with GPS jamming, a practice that blocks or spoofs satellite navigation. Originally used for military and service protection, it is now increasingly being documented as a tool for destabilization. European governments have expressed concerns that the increasing GPS jamming attributed to Russia could pose serious risks to aviation.

von der Leyen was travelling from Warsaw to Plovdiv to meet Bulgarian Prime Minister Rosen Zeliazkov and visit a defence plant.