"Online check-in gives the liberty to check-in from home/office. Online check-in starts 24 hours and ends up 60 minutes before the scheduled departure flight. In online check-in, you will receive your e-boarding pass, which you can take the print out. Web Check-in also allows you to check in your luggage in advance, select your seat, meal options (if available) and many more, before you depart for the flight.
Mobile is an easy and quick way to check-in but for that, you must have an app that is Fly Delta App. The mobile check-n starts 24 hours and ends 60 minutes before the scheduled departure time. You will get your boarding pass on your mobile device.
The airport check-in starts from 30 minutes to 4 hours before the scheduled departure flight. You will receive a print boarding pass in this option.
Note: Apart from this, you will also get to enjoy priority check-in option if you are a frequent flyer.
"