This is directly from Delta's web site:
Home Travel VCI Web FAQs Check-In FAQs
Check-In FAQs
Below are answers to some of the most frequently asked questions about check-in. If your question or comment has not been addressed, please feel free to E-mail Us.
Airport Check-In
What is the minimum gate check-in time for domestic flights?
What is the minimum gate check-in time for international flights?
What documents do I need for check-in?
delta.com Check-In
What is delta.com check-in and who can use it?
When should I use delta.com check-in?
What are the other qualifications for using delta.com check-in?
How do I check in on delta.com?
What if I don't have a PIN?
What if I have baggage to check?
What if I want to standby for an upgrade?
What if I need to make a change to my ticket/reservation?
What if I forget to bring my SkyMiles Medallion card or delta.com boarding card to the airport?
When I use delta.com check-in, when do I need to be at the gate?
Will using delta.com check-in hold my seat longer?
After I use delta.com, what happens if my plans change and I will no longer be taking the flight?
Wireless/Phone Check-In Options for SkyMiles Medallion members
How do I check in by telephone?
How do I check in on my wireless Palm Powered handheld?
How do I check in on my Web-enabled phone?
How do I use my SkyMiles Medallion card to board at the gate?
delta.com Boarding Card
I forgot to print my boarding card after I checked-in on delta.com. What should I do?
How do I reprint my boarding card if I need another copy?
What happens if I change my seat assignment after I check in and print my boarding card?
What should I do if some of the images on the boarding card are not appearing?
Parts of my boarding card are cut off when I print it. Is this ok?
Are there any other printer settings I should be concerned about?
--------------------------------------------------------------------------------
Airport Check-In
What is the minimum gate check-in time for domestic flights?
If you have a reservation for travel within the U.S. (including Puerto Rico and the U.S. Virgin Islands), you must check in at least 1 hour (excluding Delta Shuttle) before scheduled departure and be at the gate at least 15 minutes before scheduled departure or your seat may be released and reassigned.
What is the minimum gate check-in time for international flights?
If you are traveling between the U.S. and other countries including the Bahamas, Bermuda, Canada, Central America, Mexico, South America, Europe, Asia or Africa, you must check in at least 2 hours before scheduled departure and be at the boarding gate at least 45 minutes before scheduled departure or your seat may be released and your reservation may be canceled.
Please remember that the above check-in times are minimums and Delta recommends that you arrive at the gate earlier to facilitate an on-time departure.
What documents do I need for check-in?
If you have a paper ticket for a domestic flight, passengers age 18 and over must present one form of photo identification issued by a local state or federal government agency (e.g.: passport/drivers license/military ID), or two forms of non-photo identification, one of which must have been issued by a state or federal agency (e.g.: U.S. social security card). For an international flight, you will need to present a valid passport, visa, or any other required documentation. Passengers without proper ID may be denied boarding.
For e>tickets, you will need to show your photo identification and electronic ticket receipt to receive your boarding pass.
This is the link:
http://www.delta.com/travel/VCI/web/faqs/virtual_check-in/index.jsp#documents
