Flying from Skopje and nearby

Hi,
I´ve been checking the flights from Skopje to Europe and they are quite limited and expensive. Have you ever tried to fly from Sofia or Thessalonica? I was wondering if I could drive to those cities and leave the car in the airport.

How long does it take to drive to those places? Considering road conditions and border crossing... They are relatively close but I guess estimated time would be higher...

Many thanks,

Carlos