No more levels after 15th

After getting to level 15 it would say maximum levels and will longer count the poits. I still earn money and can buy stuff. But no bigger airplanes tham L and I do not know if I can get to anorher airport. Different from Barry.

You can unlock next Airport after handling enough passengers…
In the main menu, tap on “choose Airport” then see how many passengers you have handled in BRI, that number must be more then the number under it to unlock the next Airport

You have to handle atleast 117,500 to unlock PRG