I really like the game concept simple and minimal but the only issue with the game is income generated from flight are way too low. You can't progess in the game without watching ads, neither you can control the flight cost nor airport income. It's like $1/sec and it doesn't depends on no. of flight and no. of airport even if we increase then the revenue will be still $1. Hope developer will be reading the review and make the game more enjoyable.