<P> Check - in is usually the first procedure for a passenger when arriving at an airport, as airline regulations require passengers to check in by certain times prior to the departure of a flight . This duration spans from 15 minutes to 4 hours depending on the destination and airline . During this process, the passenger has the ability to ask for special accommodations such as seating preferences, inquire about flight or destination information, accumulate frequent flyer program miles, or pay for upgrades . The required time is sometimes written in the reservation, sometimes written somewhere in websites, and sometimes only referred as "passengers should allow sufficient time for check - in". </P> <P> The airline check - in's main function, however, is to accept luggage that is to go in the aircraft's cargo hold and issue boarding passes . </P> <P> In - town check - in service is a service offered by some cities such as Abu Dhabi, Seoul, Hong Kong, Delhi, Kuala Lumpur--International, Stockholm, Toronto, Vienna and Taipei, where passengers may check in luggage in designated places within the city but outside the airport . This reduces check - in time and queuing at the airport . </P> <P> At the time of check - in, one of the agent's primary duties is to check for valid documents . This includes tickets, passports, visas, letters of consent, and in some case, passengers' address and contact details to comply with immigration requirements . </P>

Does it cost money to check in at the airport