So, the actual issue that is in play is the boost being provided to new airlines that are late joiners to a game world.
In a NEW game world, all airlines start with a CI of 5 that will drop quickly if marketing campaigns are not added. If marketing campaigns are added, then over time, a 20-30 CI is achievable in say, 3-6 game months. In an ONGOING game world, a new entrant is given an initial boost, in this case, to a CI of 20, that will hold steady at the 20 as a minimum number until it is otherwise exceeded by the usual climb of marketing dollars and time spent.
Given the above function, you can throw all the dollars you want at marketing when you join an ongoing game world, but realistically, because CI is a function of both marketing AND time, you won't be in a position to exceed the initial CI floor for a while. So, what's happening is that new players that don't understand how this works are piling more and more funds into marketing to try to impact it, and seeing no apparent result and filing these bug reports.
Alba - you really shouldn't spend more than 10% of your total revenue on marketing if you expect to be profitable in this game... that should be more than enough to get you a high CI over time.