Knowing whom to trust is important in travel (and, for that matter, in life).
Up until 2 years ago, I put my trust in the airfare studies done by the Airlines Reporting Corporation (ARC). The entity has a huge reach, since it acts as the middleman between airlines and travel agents—pretty much all of them, pretty much everywhere.
ARC processes some $100 billion in airfare service transactions annually. And since the company doesn't sell plane tickets to the public, ARC is an impartial entity when it comes to consumer advice.
Alas, the ARC no longer releases a report on its airfare data. Into the void have stepped two titans of travel: Expedia and Google Flights. Each has looked at millions upon millions of airfare transactions to see what patterns exist.
But wouldn't you know it: In some cases, they give conflicting advice.
Full disclosure: I think Expedia's study, which was released in February and is based exclusively on data from 2025, may be the more accurate one.
For its report released last fall, Google crunched airfare numbers from Jan. 1, 2021, through Aug. 1, 2025, a stretch that began when the world was still emerging from the pandemic and travel patterns were shifting dramatically year by year.
In any case, here's what the two airfare studies claim.
The best time to book domestic flights
Set a calendar reminder. According to Google, booking domestic flights 39 days in advance yields the lowest airfares. Beyond that, Google says 23 to 51 days before travel is the best time period for snagging deals.
Interestingly, Expedia recommends purchasing domestic airfare 15 to 30 days before travel—a shorter booking window.
Expedia also warns that booking too far in advance leads to overpayment. According to the company's findings, flyers who booked more than 6 months out paid on average $160 more than those who booked during Expedia's recommended window.
Google is silent about booking too far ahead for domestic fares, but does give some weird advice on international flights that I'll get to in a minute.
Google offers advice by season as well. For spring break, the search giant found that booking 43 days out got the best prices. Specifically, the window for good fares was 28 to 61 days ahead.
For summer travel, Google recommends booking 21 days out, with the best fare window being 14 to 43 days ahead of travel. You may notice that this advice goes against the domestic booking window (starting at 23 days before travel) the study touts as ideal.
End-of-year travel tips vary by holiday. For Thanksgiving, nearer to that busy weekend is better, according to Google. Passengers who booked between 24 and 59 days did well, while those who put money down 35 days ahead did best.
Christmas savings could be had between 32 and 73 days in advance, per Google's study, with 51 days ahead being the ideal day to book.
The best time to book international flights
Here's where Google's advice gets odd.
In the report's summary, researchers claim that travelers who book 49 days or more (Google's italicization, not mine) before international trips find the lowest prices. No range of dates is mentioned except for travel to the Caribbean and Mexico. Google's best booking window for both: 26 to 79 days in advance.
Expedia couldn't disagree more—and I share this sentiment, having watched airfares for several decades now. From what I've seen, booking 6 months ahead is a sure way to overpay.
According to Expedia's findings, an average savings of $190 awaits anyone who books 31 to 45 days ahead instead of 6 months out.
Expedia further reports that booking 8 to 15 days ahead yields an average savings of $225. But who has the courage to cut things that close?
The best times of year and best days of the week to fly for lower fares
This is a topic Google doesn't touch. But according to Expedia's data, flying during a slower month is the surest way to save.
January is now the month with the lowest domestic airfares, the report shows—which makes sense given the travel lull after the holiday rush.
But, counterintuitively, Expedia's data reveals August to be the month with the lowest international fares.
Expedia doesn't explain why prices are dropping in August, but my guess is that it has to do with more planes being in the sky to accommodate summer travelers at the same time that traveler numbers take a dip during the last 2 weeks of the month, when so many students return to school.
Or perhaps August demand is weakening due to factors such as the intense heat waves Europe now regularly experiences during that part of the summer.
How much are international fares down in August? According to Expedia, the month's international flights are now an average of 29% cheaper than December trips. Time to reschedule Christmas?
Additionally, Expedia found that Friday is the least expensive day to fly internationally, with Tuesday taking top honors for domestic hops (14% cheaper than Sunday).
Is there a magic day of the week for booking flights?
This one harshes my travel expert buzz. For the previous 5 years, both the ARC and Expedia have reported that searching for and purchasing tickets on a Sunday snagged the best deals, and the savings were real.
This year, ARC is silent and Expedia has crowned Friday as the best day to book more affordable international airfares. Saturday is the day for domestic fares. But at savings of just 3% and 2%, respectively, who cares?
Will worldwide instability be a factor?
That's the multimillion-dollar question.
No factor affects airfares more drastically than the cost of fuel. And since some 20% of the world's fuel goes through the Strait of Hormuz, a body of water effectively shut to freighters by the current war with Iran, prices for oil are already starting to rise—and quickly.
My unfiltered advice: If you need to fly in the next 7 months, buy your plane tickets ASAP. Prices could be increasing drastically soon.