With the peak summer travel season winding down, it's time for National Cheap Flight Day.

But don't let the misleading name fool you into rushing to book your next trip.

"There's no specific day where flights are going to be at their cheapest," Katy Nastro, a travel expert at Going, tells CNBC Make. "That's just not the case." 

Instead, Nastro says that the best time to book air travel will always be in relation to when you're planning on flying. This period when the best rates tend to be found is called the Goldilocks window. 

It gets its name because it's not too far away from your travel date, but it's also not too close. For domestic travel the Goldilocks window is between one and three months before your flight, while for international flights it is between two and eight months ahead of your trip. 

However, there's more to finding affordable airfare than just getting the timing right. Here are three travel expert-approved tips for National Cheap Flights Day. 

1. Practice, practice, practice

If you know there's a trip that you want to take this year but you're not ready to buy your tickets yet, that shouldn't stop you from perusing flights. Doing this periodically in the weeks or months before you book can be help you get your bearings and set your expectations for how much you'll want to pay.

Nastro recommends using search sites like Google Flights, Skyscanner and Momondo to compare prices. 

"It doesn't matter where you're searching as long as you get a good sampling of those flights from multiple different areas," she says. "That will give you a better understanding each week and each month of what those flight prices look like." 

Gemma Jamieson, Skyscanner's senior global PR manager, says putting in the time while doing your research may help save you money in the long run.

"Airlines are being really clever about pricing and competing with each other. They're watching data, they're watching traveler behavior and they're mapping out these pockets where they can be super competitive," she says. "Doing a little bit of extra comparison, going a little bit further and shopping around for just a little bit longer than you might normally could save you lots and lots of money." 

2. Don't drag your feet

The biggest mistake you can make when it comes to searching for cheap flights is waiting until the last second in hopes that the flight you want will drop in price. This is especially true if you're starting to look at holiday travel.

"Airfare tends to go in the upward direction, especially when we're getting into peak season," Nastro says. "The holidays are when you really want to avoid booking at the last minute."

She wants to dispel the common misconception that airlines will add at the last minute just because an existing one sold out. 

"That's not really how it works," Nastro says. "There's not an endless supply of backup flights that they can just throw on the schedule."

3. Flexibility will save you money

If you don't have a set destination or dates you need to travel, you're in the best position to find the cheapest airfare possible. 

"If you're able to, keeping an open mind is the ultimate way to save money," Jamieson says. "People who have kept an open mind in the past have driven the rise of destinations like Croatia, which is now a sort of European summer vacation staple."

Likewise, Nastro says "flexibility is going to be your best friend when you're looking for a really affordable flight."

If you know where and when you need to fly, your next best bet is being flexible about what airlines you take. By limiting yourself to only airlines where you have points or status, you could be cutting yourself off from not only better rates, but also more convenient flight times. 

"You're really missing out on some great fares if you're only pigeonholing yourself to one or two specific carriers," she says. "I understand people have preference, but if your concern is finding affordable flights, opening up your scope can really help you do that."

Jamieson recommends exploring not only round-trip options, but also one-way flights in each direction to see if there are other airlines that have better rates. 

"Explore your options," Jamieson says. "Break down your trip a little bit so you're not necessarily flying out with the same airline you return with." 

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