Where do I find my Delta confirmation number for online check-in?

A few places to check:

1. Your confirmation email. Search your inbox and spam folder for “Delta” or “e-ticket receipt”. The confirmation number is usually a 6-character code of letters and numbers.
2. The Fly Delta app. If you’re logged in to SkyMiles, your trips usually appear automatically.
3. Your booking site. If you booked through an agency, the airline’s code may be shown in your booking details.
4. SkyMiles number. You can often start check-in with your SkyMiles number and last name instead.

If you still can’t find it, contact the agency or Delta support. More on Delta online check-in is explained here.