American Airlines flights are stopped do to Sabre outage. I am trying to get from MSP to Ord for a connecting international flight. Thinking about booking a later today Delta flight as a backup. What would be the Delta cancellation fees if I cancelled the Delta flight last minute? Thanks!!!

No penalty or fee to cancel tickets booked online with Delta (or DL phone reservations) within 24 hrs or purchase.

Does that apply to same day flights? I always thought there were exclusions within a number of days before the flight.

"As part of our Customer Commitment, you can get a refund for most eTickets purchased directly through Delta for travel originating in the United States, U.S. Virgin Islands, Puerto Rico, and Canada. You don’t even have to call.
Once you've bought a qualifying eTicket, you have a day to cancel it for any reason and receive a full refund—including any prepaid fees and Direct Ticketing Charges—with no cancellation fee.
See full terms and conditions for additional details.
Here’s how it works:
Use your name and flight confirmation number to search for your itinerary. Then, cancel your eTicket. Your refund will be automatically applied to your original form of payment.
If you purchased your eTicket at a Delta ticket office or airport ticket counter, email your receipt number (beginning with 006) for a refund of the Direct Ticketing Charge.
TERMS & CONDITIONS
Tickets/Cancellation:
Cancellation request must be made by midnight of the day after the eTicket is purchased or midnight of the departure date of the first flight, whichever comes first. Available only for eTickets purchased at the time of reservation through Delta ticket offices and airport ticket counters, Reservation Sales, or at delta.com.
Validity:
Valid for travel originating in the United States, U.S. Virgin Islands, Puerto Rico, and Canada, regardless of where the eTicket is purchased.
If you wish to pay for your ticket with any paper currency—such as cash, or check, Delta Dollars, or denied boarding voucher—you may make the reservation over the phone, which will guarantee the fare for 24 hours. Your ticket must be purchased at a Delta ticketing location by midnight of the following day, or your reservation will be cancelled. Once purchased, these tickets will not be eligible for cancellation under the Risk-Free Cancellation policy.
Does not apply to travel agency tickets and bookings, paper tickets, or partially-flown reissued tickets. For SkyMiles Award tickets, please call Delta Reservations to request cancellation.
Miscellaneous:
Cancellation request does not need to go through the same area in which the eTicket was purchased. For example, if you purchase via Reservations, you can cancel through delta.com.
Fares, offers and rules are subject to change without notice."

https://www.delta.com/content/www/en...cellation.html

If a person books a flight today and then cancels it... its within 24 hour policy to get a FULL REFUND back to original payment. You can cancel the ticket within 10 minutes of flight. If done by credit card the refund will take 3-7 business days before showing up back on the credit card statement.

Yeah, maybe not. According to Delta's T&C (bolding mine), it looks like midnight on the day of departure is the cut-off: