Niš Constantine the Great Airport — Niš, Serbia

INI takes its name from Constantine the Great, the Roman emperor credited with legalizing Christianity across the empire, who was born in the ancient city of Naissus on the site of modern Niš. For much of its history a quiet regional airfield with limited scheduled service, the airport transformed over the past two decades as low-cost carriers, including a dedicated Wizz Air base, added routes connecting southern Serbia to Western Europe, drawing on both tourism demand and the large Serbian diaspora working abroad. Niš itself ranks as Serbia's third-largest city, known for a preserved Ottoman-era fortress, Roman archaeological remains, and a university that anchors much of the local economy alongside manufacturing. Passenger numbers at INI have grown considerably faster in percentage terms than at Serbia's larger Belgrade hub, reflecting the airport's shift from a sleepy backup field into a genuine low-cost gateway.