A check-in method for airlines allows passengers to use Short Message Service (SMS) to check-in themselves and baggage. A passenger requests to check-in via SMS from practically anywhere and not limited to the airport. After receipt of the request, a confirmation message is sent back to the passenger's registered mobile phone number by SMS. The system will ask the passenger for, and receive from the passenger, the number of bags they intend to check-in for the flight. The passengers can in some embodiments drop the baggage off without any required further action. The system issues an SMS-based cryptographically secure code, such as a bar-code boarding pass to the passenger once the baggage (if any) is successfully transferred and registered to existing baggage management systems through the process above. This code, when scanned, recognized and authenticated provides identification and security clearance for the passenger to board the aircraft.