I don't see Putin doing that. Russia has always used the UN to block US action, but has never used it to approve its own actions.
He would have to get transit rights from a neighboring state to get to Serbia. He has no direct land or sea route to Serbia.
I suspect he would have no qualms about using Albanian airspace to accomplish that objective. I don't think Putin is going to be asking the surrounding countries for permission to fly over their countries. He's just going to do it.
This could get really ugly.