Planning for a trip can sometimes be just as much fun as actually taking it. One of the most important things to do before heading out on vacation is to book flights. There are a few pieces of information that are needed to make an airline reservation online, which is how most passengers book these days. Just be sure to have all travel documents handy and do some planning before selecting your flights.

Dates and Times of Travel

The first information needed to book a flight are the dates of travel and preferred flight times. If your itinerary is set in stone, search using those dates. For those who have some flexibility, it's worth it to do a more extensive search to find cheaper fares or better flight times. Departing on a weekday, for example, is often cheaper than leaving on a weekend when flights can be busier. Think about what time you'd like to arrive at your destination when selecting a flight time and take stops or layovers into consideration as well. Sometimes it's more about arrival time than departure time.

Airport Choice

When traveling into and out of a bigger city, it's worth looking into several different airports. For example, when traveling via Los Angeles, check flights through Burbank Hollywood Airport instead of LAX. Having some flexibility will help you find the best fare and options for air travel. Some airlines have hubs in specific airports, which can also help decide which is right for your itinerary. Because Delta, for example, is based in Hartsfield-Jackson Atlanta International Airport, it will have more options there.

Personal Information

Input each traveler's personal information, including full name, date of birth, email address and phone number when booking a flight. You'll need to indicate whether any traveler is under 18 years of age or is a newborn or infant being held in a lap. Be sure to enter each name as it appears on the passenger's official government-issued ID so the ticket matches. If a passenger has a Known Traveler ID number, which is given to those with Global Entry or TSA Precheck, add that to the booking, as well as any frequent-flier membership numbers.

International Travel

When traveling outside the U.S., each passenger will need several pieces of passport information. Insert your passport number, country of issue and expiration date, as well as your legal full name, when booking an international flight. That information can sometimes be added later or typed in during online check in. Be sure your passport has at least six months of validity prior to its expiration. Most destinations also require at least one full blank page for stamps and visas.

Payment Information

Travelers will, of course, need to pay for the flight when booking it. Have a credit or debit card ready so you can provide the card number and expiration date, as well as the cardholder's name and billing information. Most airlines will also give the option to add travel insurance to the reservation, which can help if your plans might change or be impacted by poor weather. Opt in if it makes sense for your trip.