Some of the busiest travel days of the year are upon us, and if you’re like more than 31 million other Americans, you’re heading to an airport and flying somewhere over Thanksgiving.

So the question becomes, as you’re waiting in traffic or a security check line: Where do you want to go next — for fun, and preferably, for cheap?

George Zeng, cofounder of the flight-finder website Moonfish.com, has some tips for that. The Wharton grad and former product lead at Facebook launched the site earlier this year to sift through billions of flight records and surface really good deals.

To wit: $320 to Madrid, $340 to Paris, and $50 to Miami — all round-trip flights from Philly, as of Monday afternoon, and all more than 65% off the expected fare, according to Moonfish.

There’s a free version of the site that focuses just on travel out of Philadelphia International Airport and a subscription-level service that searches for deals from a handful of other cities — Newark, Trenton, Atlantic City, Harrisburg, and Allentown — in addition to PHL.

How can travelers find great deals on flights?

For Zeng, this boils down to two words: Be flexible.

“The best way for a consumer booking a trip to find value is to have flexibility,” he said.

That goes for your point of origin — can you leave from Newark or Baltimore, instead of Philadelphia? — and for your destination and travel dates, too.

For instance, you might have a specific destination in mind, but if the purpose of your trip, really, is to spend time on a pretty beach, you might be able to find a much cheaper flight to Turks and Caicos, then to Thailand. “Being open to different destinations dramatically increases your chance of getting a good deal,” Zeng said.

Same goes for travel dates. Someone might have a trip to France in mind for May 2020, flying in and out of Paris. But if that person could save $200 by shifting the trip to late April, or perhaps flying through Nice instead of Paris, Zeng has found that travelers are often open to those changes.

“Building in that flexibility in their own expectations is a really good way to get better deals,” he said.

How do prices change depending on how soon, or how far in advance, a flight is? When’s the sweet spot for finding good prices on tickets?

About six to 12 months before a scheduled flight, “prices are pretty stable,” Zeng said, adding: “At six months, prices can go up or down depending on supply and demand dynamics.”

That can be a good thing and a bad thing. It means if you want to lock in a price for a flight, you should consider buying a ticket about six months in advance.

Or, you can “roll the dice a little bit,” Zeng said, and see if fares drop. Just bear in mind that around the one-month mark, he says, prices start to increase.

There’s an exception to this timetable: booking flights for major holidays. Around the Fourth of July, Thanksgiving, Christmas, and New Year’s, “fare prices tend to be high and stay high, even really far out,” Zeng said. “So probably the best thing to do is book out as far as you can” in advance.

(An exception to the exception: If you’re willing to travel on days when other people usually don’t, such as on Dec. 24 or Dec. 31, then you might be able to score a cheaper flight, Zeng pointed out.)

Is it a given that low-cost carriers will always have better deals than other airlines? Or are there times when prices are on par?

“The way I think about it: If you just bring a personal item, generally these discount airlines will always be cheaper,” Zeng said.

But if you need to bring more than a bag that can fit under the seat, then be mindful of additional fees, which can add up.

For example, if you’re flying Frontier, the fees to bring a carry-on bag (in addition to a personal item) typically range from $35 to $60, Zeng said. (The prices vary by flight.) Whereas with American Airlines’ basic economy, one carry-on bag is free.

“Read what those restrictions are,” Zeng advised, and if possible, travel light.

What destinations are popular with Philly travelers right now?

Daydreaming about going to Europe? Or someplace that’s ... sunny? According to Zeng, these are the top 10 destinations that Moonfish users have been searching over the last two weeks or so. (The company does not release numbers on how many users it has.)

  1. London (LHR)
  2. Dublin (DUB)
  3. Paris (CDG)
  4. Rome (FCO)
  5. Madrid (MAD)
  6. Frankfurt (FRA)
  7. Barcelona (BCN)
  8. Los Angeles (LAX)
  9. San Juan (SJU)
  10. Las Vegas (LAS)