COPENHAGEN, Denmark (AP) — Finland’s national carrier Finnair said Thursday that it will resume flights to Estonia’s second largest city in June after two of its planes were prevented from landing in Tartu last month because of GPS disruptions.

The cause of the GPS interference that forced the two flights to return to Helsinki on April 25 and April 26 was not immediately known. Estonian officials blamed the jamming in the region on Russia.

Finnair said Tartu Airport now uses radio signals sent from ground stations instead of GPS signals to direct plane landings.

Jari Paajanen, head of Finnair’s operations control, thanked the Estonian Air Navigation Services for finding an alternative method “so swiftly.”

The airline said earlier this month that it was suspending flying to Tartu until May 31 because of the interference. The Finnish carrier, which is the only airline operating international flights to Tartu, has flights from Helsinki to Tartu twice a day, six days a week.

The airline said GPS interference has significantly increased since 2022. Earlier Finnair said interference has been reported “especially near Kaliningrad, the Black Sea, the Caspian Sea and the Eastern Mediterranean.” Estonian Foreign Minister Margus Tsahkna has said that the jamming was carried out by Russia and could eventually lead of a crash, adding that “this can be considered as a hybrid attack.”

Finnair said its aircraft systems detect GPS interference and its pilots are “well aware of GPS interference and know how to prepare for it.”