Surprisingly, most airports make the majority of their profit from non-aeronautical revenue rather than the flights themselves. While airlines pay "landing fees" and "terminal leases," these often just cover the operational costs of maintaining the runways and gates. The real "cash cows" for an airport are parking fees, car rentals, and retail concessions. Every time you buy a $15 sandwich, pay for long-term parking, or walk through a Duty-Free shop, the airport takes a significant percentage of those sales. In fact, for many large international hubs, non-aeronautical revenue accounts for over 50% to 60% of total income. This is why modern airports look more like shopping malls with runways attached; the more time passengers spend in the terminal "dwelling," the more money the airport makes. Property development and advertising also play massive roles in the financial health of an airport, allowing them to remain profitable even when flight volumes fluctuate or when they offer lower fees to attract new airline carriers.