Lufthansa allows passengers to check in 24 hours before departure for most flights. This applies to both domestic and international flights, including those within the Schengen Area. Passengers can check in via the Lufthansa website, the Fly Lufthansa app, or self-service kiosks at the airport. For flights departing from Germany, the check-in window opens 23 hours before departure. Additionally, Lufthansa offers an automatic check-in service for passengers flying within Germany and across Europe. If the booking was made at least 24 hours in advance and the passenger has entered their personal details and preferences in their Miles & More account or Lufthansa iD, they will receive their boarding pass automatically via text or email 23 hours before departure. 

For long-haul flights, especially those departing from non-Schengen countries, passengers are advised to check in at least 24 hours before departure. It's important to note that check-in times may vary depending on the departure airport and destination. Therefore, it's recommended to verify the specific check-in time for your flight on the Lufthansa website or by contacting Lufthansa customer service.

In summary, Lufthansa generally allows check-in 24 hours before departure, with some variations depending on the departure location and destination. Utilizing online check-in options can save time and streamline the travel experience.