Don't know if I'm doing something wrong, or if the gameplay changed, but after a few hours the cost to continue upgrading anything is in the millions and I can't see any way to get that much other than IAPs. 63m to go from 2* prestige to 3* with flights making maybe 100k, even with the 2x video ad multiplier??? Perhaps it's the "Idle" concept of gaining money while the game isn't running, but then what's the point? Uninstalled.