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Here's why you should never wait to buy plane tickets on National Cheap Flight Day

Viktoryia Vinnikava | Twenty20

Going on vacation? Don't wait to buy your next flight until National Cheap Flight Day. Despite the name, one airfare expert says Friday, Aug. 23, is probably not the best day of the year to score the cheapest flights.

Started in 2015, the day marks when airlines begin to reduce ticket prices as the summer travel season wraps up. But Scott Keyes, co-founder and CEO of Scott's Cheap Flights, says the data around National Cheap Flight Day is "fundamentally flawed."

"Flights are generally less expensive in fall than in summer, you'll get no argument from me," Keyes tells CNBC Make It. But that doesn't mean you should wait to book all your flights until the end of August. The best day for flight deals last year doesn't have any predictive power on what will be the best day for flight deals this year.

"Flight deals can pop up completely at random," he says. In fact, Keyes says the best deal his company found last year — round-trip flights from Los Angeles to a variety of cities in Southeast Asia in business class starting at $560 — appeared on Aug. 16, a week before National Cheap Flight Day.

"The bad news is that there's not any single cheapest day of the year to book flights, but the good news is that right now we're living in the golden age of cheap flights," Keyes says.

Rather than relying on a particular day of the year, Keyes says there are a few things budget-minded travelers can focus on when searching for a good flight price.

Don't wait too late to book

To really increase your chances of scoring the best prices on flights, Keyes says you should plan to book ahead. He recommends purchasing tickets for domestic flights one to three months in advance and two to eight months ahead for international trips.

"There's a temptation to think there are last-minute deals that will pop up or you can get a standby flight — those basically don't exist anymore," Keyes says. Instead, prices tend to skyrocket a week or two before a flight's departure because airlines know that's when business travelers who don't have the same budget constraints tend to book.

Jump on any deals you see

If you see a good deal, don't delay purchasing it. Keyes says in general, the better the deal, the less time it will likely last.

"It can be a bit frustrating," Keyes. For example, last year's deal on business class flights to Southeast Asia was only around for four hours, Keyes says.

That's why it can help to set up alerts for any flights you're considering, so you'll know as early as possible when the price drops. On sites like Google Flights, Kayak and Skyscanner, or on the Hopper app, you can set up price alerts on specific routes.

You can also sign up for airfare deal newsletters, including Scott's Cheap Flights, Fly (Almost) Free and Next Vacay. The first two offer free versions of their newsletters, while NextVacay starts at $25 a year.

"You never know exactly how long any given deal is going to last because these tend to be mistake fares and unadvertised sales," Keyes.

Skip airfare 'sales'

In general, advertised airfare sales don't offer really great deals. It's not that these airfares can never be a good deal, but they typically aren't the lowest prices.

"As a traveler, do yourself a favor by ignoring them," Keyes says. At a high level, you need to ask yourself why an airline would have these types of sales. The short answer: They don't think the fares are going to sell themselves, so they're putting marketing dollars behind them, Keyes says.

Really good airfare deals are going to sell themselves. "You don't need to do any marketing because you don't need to convince people on it, they're already convinced," Keyes says.

Budget airlines aren't always the best deal

Airlines like Norwegian Air and Frontier will likely have cheaper flights than the legacy carries like British Airways or Delta, but you're probably going to give up some amenities and comforts in order to save that money.

Before booking on a budget airline, it's worth carefully reviewing what's actually included in the ticket price — onboard food and entertainment may be extra, even on trans-Atlantic flights — as well as the baggage size, weight and amount limits. 

You may also want to check if the airline is part of an alliance or has any partnerships. Typically, when it comes to budget airlines, "when things go bad, they can go really bad," Keyes says. Many times that's because these airlines have fewer routes and partnerships, so if you're flight gets cancelled at the last minute, you may be waiting days or even a week for the next available seat.

Don't miss: 5 things you need to know about booking a budget airline ticket, according to experts

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