In SimCity 4, the international airport has the highest capacity out of the three default airports in SimCity 4. Like all default airports, the building has three upgrades, upgradeable once the building is near its capacity.
In SimCity (2013), the international airport is a great work building, which is unlocked by having 100 tourists arrive at a municipal airport. In order to build it, the starting player must have 1 million simoleons in their treasury.
After that, players in the cluster the great work was started must provide 2,000 tons of metal, 1,500 tons of alloy, and 250,000 barrels of crude oil must be provided, after which workers must be supplied in order to finish the great work.
The great work, once built, provides tourists as well as providing a place for freighters to export their goods.