Air France cancelled another flight from Paris to Moscow on Friday after Russia rejected a flight plan that would have skipped Belarusian airspace, the airline said.
A flight was scrapped on Wednesday for similar reasons as the EU has urged airlines to avoid Belarusian airspace after the regime there diverted a Ryanair plane and arrested an opposition journalist on board.
Austrian Airlines on Thursday also had to cancel a flight from Vienna to Moscow that would have avoided Belarus.
Air France said Friday that flight AF1154 was cancelled "for operational reasons related to bypassing Belarusian airspace, requiring a new authorisation from Russian authorities to enter their territory".
EU foreign policy chief Josep Borrell said earlier that the bloc was monitoring whether Russia was systematically refusing to let European airlines land if they avoided Belarus.
"We don't know if it is case by case, specific cases, or is a general norm from the Russian authorities in order to make the European planes overfly Belarus," Borrell told journalists.