To book a Delta Airlines flights, go to the official Delta Airlines site and select the 'book' option. Fill in the departure and arrival airports, as well as the trip type. It could be a one-way, round-trip, or multi-city. Now, fill in the departure date, and the total number of passengers. Note: If you cancel your flight, the refundable rates will return you a portion of your fare. Using the shop with miles feature, you may purchase your travel with points earned, and selecting the 'my dates are flexible' option will help you find the cheapest Delta flights. All of these options can assist you to narrow down your search. For the check-in, you have got two options. Either you can do so from the comfort of your home through online check-in or visit the airport for the same. The online method starts just 24 hours before the flight time.