Singapore Airlines check-in policy allows passengers to check in online, via mobile app, or at the airport. Online check-in is available from 48 hours up to 1.5 hours before departure, where passengers can select seats and obtain boarding passes electronically. Mobile check-in follows a similar timeline and process. At the airport, check-in counters open 3 hours before departure and close 40 minutes prior. Baggage can be dropped off during online/mobile check-in or at the airport. For international flights, it's recommended to arrive 2.5 to 3 hours before departure. Check-in is completed by entering booking details online, selecting seats, and obtaining boarding passes. At the airport, check-in involves presenting necessary documents, selecting seats if not done online, and receiving a printed boarding pass. Familiarize yourself with Singapore Airlines check in policy to ensure a smooth travel experience.