The European air traffic control service has been subjected to a cyberattack by pro-Russian hackers, according to a representative of the European organization for the safety of air navigation, also known as Eurocontrol.

The attack on the site has been causing access issues since April 19, the spokesman noted, while stressing that “there was no impact.” There were problems until the evening.

A senior Eurocontrol official with knowledge of the situation told the WSJ that the agency had secured its operating systems and that there would be no air safety issues. He added that some of the roughly 2,000 employees used WebEx to communicate.

Eurocontrol is an important part of air traffic safety in Europe, managing cross-border traffic in the airspace covered by national air traffic authorities. In addition, its office in Maastricht, The Netherlands provides direct upper air traffic control for that country as well as Belgium, Luxembourg and northwest Germany for both civil and military flights.

European authorities are concerned that Russia could attack parts of Europe’s transport, communications and energy infrastructure, sparking the biggest showdown with the West since the Cold War.

According to the WSJ