Planes flying in the vicinity of Israel’s Ben-Gurion International Airport have been unable to use their satellite navigation systems for the past three weeks due to a possible cyber-attack, the country’s Airports Authority revealed on Wednesday.

Officials have not yet determined what is causing the problem, which has a “significant impact on all aspects of operating a plane from the cockpit, as well as on managing air traffic,” said an AA spokesman in a statement.

The Israeli Airline Pilots Association said it suspects the airport is suffering from a “spoofing” attack, in which false data is fed to GPS receivers through a transmitter to falsify location information, making it appear to pilots that their aircraft are in a different location than they actually are.

The association said that while numerous countries have the technology to conduct spoofing attacks, it was unlikely that any terrorist group did.

The association also noted that it believes it knows which country is causing the problem, but would not release the name at this time.

However, Israeli sources have told i24News that it is likely Russia that has been responsible for the GPS disruptions. While the sources are not clear on how Russia was conducting the interference, they said it was likely due to Russian interference originating in Syria.

Israeli government bodies have opened an investigation, and Ben-Gurion has switched to the Instrument Landing System since the attacks began, a precision runway approach aid based on two radio beams that provide pilots with both vertical and horizontal guidance during an approach to land.

“It is a safe and professional method that is used every day in airports around the world, including Israel,” the Airports Authority assured travelers, noting that “at no point has there been a safety incident connected to this GPS interference or related to navigation instructions or flight paths.”