On their website, delta.com, you may purchase airline tickets for Delta. Delta offers a comprehensive and user-friendly online payment system. You may also call the Delta Airline ticket offices to make a reservation if you are unable to pay online. Additionally, approved third-party travel agents are available online and offline for the purchase of Delta Airlines tickets. Now if you want to book a delta flight in advance so you question arise in your mind that How Far in Advance Can I Book a Delta Flight? So its simple answers is that 331 days before departure you can book a ticket in delta airline.