Airbus SE said Russian airlines are flying more domestically than before the pandemic, raising concern that they’re doing so without the necessary maintenance requirements because import sanctions prevent the aircraft from receiving spare parts or software upgrades.

“We are worried about the conditions for maintenance as actually the planes are flying a lot,” Airbus Chief Executive Officer Guillaume Faury said on Friday as the manufacturer reported earnings. “Because of the sanctions, we cannot really monitor and support as we do with our customers in normal times. And that’s something that is indeed creating some concerns on the safety side. Now, there’s not much we can do about it.”

Airlines in Russia are operating about 85% of 2019 capacity this winter, according to OAG data, although that’s with a large chunk of the country’s international links cut off. Sanctions that were brought in soon after the February invasion of Ukraine prevent manufacturers from being able to support Russian airlines, although carriers continue to operate their fleets of aircraft made by Airbus as well as Boeing Co. 

Aircraft lessors have also been caught up in the fight as roughly 400 jets that had been leased to Russian companies are barred from leaving the country without state permission.