Spare the obvious WN where your boarding position is based on check in and the tickets that you are unable to select your seat on, is there any actual benefit to checking in ASAP? Some airlines automatically check you in 24 hours before your flight (NH). Is the benefit for the customer or the airline? I'm taking a wild guess and thinking that it probably helps the airline know if a seat will be vacant or not and will let them reassign your seat to someone else on the standby list, but other than that I personally cannot see a difference in checking in 24 hours online or 2 hours before my flight at the ticket counter. I see a benefit in getting my boarding pass online/mobile if I don't have any luggage to check, but I usually get a printed boarding pass when I drop my luggage anyways and sometimes I don't have internet access to get a boarding pass.