State-controlled Air Serbia will maintain its controversial flights to Russia “as a matter of principle,” even as frequent bomb threats make the routes unprofitable, President Aleksandar Vucic said Monday.

Virtually every outbound flight to Russia has received anonymous threats since most of Europe closed its airspace to Russian carriers, causing delays or requiring the plane to return to its airport of origin for security checks, Vucic said in a live interview on Pink TV. 

Serbia is among a handful of European countries that haven’t joined international sanctions against its traditional ally Russia for its invasion of Ukraine, and its flagship carrier continues to fly to Moscow and St. Petersburg. 

In early March, Air Serbia doubled its flights to Russia due to increased demand following the blockade but later reverted to its pre-war schedule after criticism. Vucic complained at the time that airlines in Turkey, the United Arab Emirates and Qatar that fly to Russia weren’t subject to the same scrutiny. 

Serbia is a candidate for European Union membership and has condemned Russia’s actions in Ukraine.