Don Mueang International Airport — Bangkok, Thailand

Opened in 1914, DMK ranks among the oldest airports still operating anywhere, having witnessed the entire arc of commercial aviation unfold from propeller biplanes to the low-cost jet carriers dominating its gates today. For decades it stood as Bangkok's sole major airport, but its role shifted dramatically after Suvarnabhumi Airport opened in 2006 to handle the bulk of international and full-service traffic, leaving Don Mueang to reinvent itself as Southeast Asia's leading base for budget carriers like AirAsia and Nok Air. The Royal Thai Air Force continues sharing the airfield, maintaining a military presence alongside the bustling commercial terminals. Located north of central Bangkok, DMK's continued relevance despite the newer airport's opening shows how quickly the region's low-cost travel boom reshaped Thai aviation.