Banja Luka has an international airport (Banja Luka International Airport, BNX) with scheduled flights from several European cities, particularly during summer. The most reliable connections are from Belgrade, Vienna, and Germany. Ryanair has operated seasonal routes, though schedules change — check current offerings before planning.
By bus, Banja Luka is well connected to Sarajevo (roughly 2.5–3 hours), Zagreb (3–4 hours), and Belgrade (4–5 hours). The bus station is central. Train service exists but is slower and less frequent than bus; the overnight train to Zagreb is comfortable if you have the time.
By car from Sarajevo, the main route follows the M-17 northwest through the Vrbas valley — a spectacular drive through the river gorge that will tempt you to stop at the rafting sections. From Zagreb the motorway gets you as far as the Croatian border, and then it is another 40 minutes on good roads.