Newly Opened Metro Line in Chengdu, China Connects Two International Airports
https://www.google.com/amp/s/www.fox19.com/prnewswire/2023/12/01/newly-opened-metro-line-chengdu-china-connects-two-international-airports/%3foutputType=amp
As far as I know, I guess the only rail line which directly connects two international airports used to be A'REX in South Korea, except for the train between Narita Airport and Haneda Airport which runs multiple rail lines.
But, Chengdu Metro Line 19 was added to the rail line connecting two international airports directly.
