If you forgot to include your middle name on a Delta ticket, you likely do not need to worry for domestic travel within the United States. TSA and Delta generally allow passengers to board as long as the first and last names on the boarding pass exactly match the government-issued ID. While Delta’s official policy recommends providing your "full legal name" (first, middle/initial, and last), the Secure Flight data transmitted to the government is the most critical part, and missing a middle name on the ticket rarely triggers a security rejection. However, for international travel, where passport requirements are much stricter, a mismatch can occasionally cause issues with automated visa checks or biometric gates. If you are concerned, you can contact Delta to add the middle name to your "Secure Flight Passenger Data" without necessarily reissuing the ticket, though most frequent flyers find that a missing middle name is a non-issue at the airport.