The nearest airports are in Semarang and Solo. From either city, take a bus heading in the opposite direction (Solo-bound from Semarang, or Semarang-bound from Solo) and tell the conductor you want Salatiga. The trip from Semarang takes about 45 minutes by taxi, slightly longer by bus. From Solo it is about an hour. You can also fly to Yogyakarta and connect by bus via Solo.