good question patson.
i think the game is so niche in its current state that it's really hard to figure out just how to promote airline club
for me there's two ways to look at it. 1. this is a beta/alpha mock-up of the game where youre testing gameplay mechanics and learning how to implement your ideas. somewhere in the future is a plan to build a fuller version of the game with a graphical UI, animations, and sound to attempt to reach more of a mainstream (but still niche tycoon/strategy) market, on a larger platform like steam/iOS/android
2. you keep the game as it is and keep improving it. if that's the case i would turn to youtube and find gaming channels that promote business sim/tycoon/indie games and invite them to play the game with an accelerated account that has stuff set up for them. maybe ask them what would be needed to get a mention in some of their videos. maybe scour some of the few remaining gaming sites and find an editorial writer or indie reporter to try out the game and make a write up.
consider what restaurants are doing with yelp and maybe you could offer current players some sort of incentive reward (im thinking cosmetic) for posting about the game on reddit or some other social media/forum. famously RIOT GAMES had a player referral system where famous youtuber totalbiscuit was able to name a playable champion in the game.
i dont think there is a good answer to your question and im almost certain theres no easy answer. promoting airline club will likely take hard work and a decent amount of creativity, perhaps moreso than simply creating the game. i commend you on all your hard work patson and wish you nothing but success