Yes, you can absolutely use your Delta SkyMiles to book a flight for someone else, even if you are not traveling with them. When booking on Delta's website or app, you simply select the option to "Shop with Miles" and enter the other person's name and details as the passenger during the checkout process. The miles will be deducted from your account, but the ticket will be issued in their name. This is a very common way to "gift" travel. However, you should never "sell" or "barter" your miles to a stranger, as this is a major violation of Delta's terms and conditions and can lead to the permanent closure of your account and the cancellation of the tickets. While you can also "Transfer" miles directly into someone else's SkyMiles account so they can book it themselves, Delta charges a fee (usually $0.01 per mile plus a processing fee) for this service, making it much more cost-effective to just book the ticket for them from your own account.