When can I check in online for my flight?
Most scheduled airlines and all low-cost airlines offer online check-in. Online check-in allows you to edit your boarding pass and select a seat (if you haven't already done so).
"Regular" airlines:
As a general rule, online check-in is available from 24 hours before departure. Some airlines allow this service from 30 hours before departure (e.g. Air France).
"Low-cost" airlines:
Depending on the airline and the extras purchased (seats/meals/priority), you can check in and obtain boarding passes as early as 30 days before flight departure.