Here's some good news for holiday travelers: Atlanta air fares for Thanksgiving travel are 33 percent below the national median, according to a report from travel marketing firm Sojern.

Among some of the nation's busiest airports, the most expensive places to fly out of this Thanksgiving are New York's John F. Kennedy International and San Francisco International, Sojern said, while Atlanta was the most affordable out of a list of 18 U.S airports.

Sojern says the findings come from data it gets through its partnerships with travel firms.

But when it comes time to take to the skies later this month, travelers out of Atlanta should also be prepared for crowds and long lines.

Delta Air Lines is warning that Thanksgiving travelers through Atlanta's airport  "will experience a greater than normal volume of traffic in the airport."

November 18, 2014 Atlanta - Travelers wait at baggage claim area at Hartsfield-Jackson International Airport on Tuesday, November 18, 2014. HYOSUB SHIN / HSHIN@AJC.COM

Credit: Kelly Yamanouchi

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Credit: Kelly Yamanouchi

Atlanta-based Delta's travel advisories including this message for Hartsfield-Jackson International Airport: "It will take longer than usual to get through the TSA security lines. It is suggested that you plan accordingly and arrive early — at least 1 1/2 hours before departure in order to get to your flight on time."