Yes, it is possible to book a flight for someone else using an Expedia account. When making the reservation, you simply need to enter the traveler's details in the flight booking form instead of your own. During the booking process, there are sections where you provide the name, contact information, and any other required details for the individual who will be traveling. It is important to ensure that the information you input matches the identification documents of the person who will be flying, as airlines typically require the ticket to reflect the traveler's name accurately.
Keep in mind that the traveler will receive any confirmations and notifications related to the flight at the email address you designate during the booking process. For any further assistance or inquiries regarding the booking process, it may be beneficial to browse the current web page for additional options or guidelines.