İstanbul Atatürk Airport — Istanbul(Bakırköy), Turkey

ISL once handled essentially all of Istanbul's scheduled international air traffic before the opposite fate befell it in April 2019, when nearly every commercial passenger flight shifted overnight to the newly built İstanbul Airport across the city. Located on the European side near the Bakırköy district along the Sea of Marmara, the airport carried the name of Mustafa Kemal Atatürk, founder of the Turkish Republic, and served for decades as Turkish Airlines' primary base as the carrier grew into one of the world's largest network airlines. Rather than closing outright, ISL has continued operating on a reduced basis, hosting cargo flights, general aviation, government and military aircraft, and occasional large-scale public events staged in its now-emptier terminal halls. Its enormous former apron and runway infrastructure remain largely intact, a visible reminder of the airport's earlier role as one of Europe's busiest gateways before traffic relocated elsewhere.