The number of days in advance you can print your boarding pass depends almost entirely on the airline’s policy, as there is no universal rule.
However, here is a general breakdown:
Some airlines allow check-in earlier than 24 hours, but it’s less common: Some U.S. Carriers: Airlines like Southwest and Alaska Airlines typically open check-in exactly 24 hours before departure. Some International/Full-Service Carriers: Airlines such as Lufthansa, KLM, and British Airways often allow check-in up to 23-30 hours in advance, but policies can vary. Status/Class of Service: Passengers with elite frequent flyer status or those traveling in premium cabins (First or Business Class) may be granted earlier check-in access, sometimes up to 36-48 hours in advance.