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It's the unofficial kick-off to the summer travel season, and automobile club AAA predicts 2.5 million people will take to the skies over Memorial Day weekend alone. That's a decrease from last year, but don't think you're going to breeze through the check-in line and airport security, especially if you're flying out of one of the airports below.

FourSquare has analyzed check-in data to find out which of our nation's airports will be the busiest over the upcoming holiday weekend. Is one of these airports in your travel plans? Let us know where you're traveling, or not traveling, over Memorial Day weekend in the comment section below.

So pack your bags (but not too many, you don't want to be charged), remember your sunscreen (3oz or less if you plan on only taking a carry-on), and put on your flip-flops on (after all, they're easy to take off at airport security). Summer is finally here!

Top 10 Busiest Airports for Memorial Day Weekend 

1. Hartsfield-Jackson Atlanta International Airport The world's busiest passenger airport won't get a break this Memorial Day weekend. As a Delta hub, there's a good chance you'll be flying through ATL if you're on a Delta flight.

2. San Francisco International Airport SFO comes in at No. 2 this Memorial Day weekend. Tip: morning flights are frequently delayed due to fog; book a mid- or late-morning flight instead.

3. Chicago O'Hare International Airport It's coming in at No. 3, but because it's a major hub, bad weather in Chicago can ground flights all over the country. Hopefully the weather will cooperate this Memorial Day weekend.

4. John F. Kennedy International Airport It'll be the busiest of the three major New York City-area airports. Flying out of LaGuardia or Newark? You're not off the hook, they're just a little further down the list.

5. McCarran International Airport Bet on crowds at the Las Vegas airport, coming in at No. 5 on Foursquare's list; it's also the No. 1 summer destination on Orbitz's top 10 list of summer destinations.

6. LaGuardia Airport Over 24 million people flew out of New York's LaGuardia Airport last year. It's just eight miles from Manhattan and the favorite area airport of many New Yorkers.

7. Denver International Airport The best part of Denver International Airport is the volunteer airport greeters, there to help with all your airport questions. Look for the white cowboy hats!

8. Boston Logan International Airport If Boston's too crowded or too expensive this Memorial Day weekend, try the nearby airport in Providence, RI. It's usually less crowded and sometimes cheaper.

9. Seattle-Tacoma International Airport The airport's website claims it's the 17th-busiest overall, but this Memorial Day weekend it's expected to come in at No.9.

10. Newark Liberty International Airport Rounding out the top 10 is EWR. Even though it's in New Jersey, it's a popular choice for New Yorkers as well, especially for international flights.