Some countries require personal information known as Advanced Passenger Information(API) or Advanced Passenger Information System(APIS) from all visitors.
However, as some countries have agreements that allow travel between them without customs and immigration, such facilities are not a definitive need for an international airport.
There are some countries such as China that are trying to ban them, but it is very hard to outlaw software that changes your computer's locations and encrypts all your online activities.
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