We Booked 50 Round Trips to Find Out When Flights Are Actually Cheapest — The Results Surprised Us

Ask ten people when you should book a flight and you'll get ten different answers. Tuesday morning before 9 a.m. Wednesday at midnight. Six weeks out. Three months out. Never on a Friday. Always on a Sunday. The conventional wisdom around flight booking timing has taken on the quality of folk mythology — passed down, repeated confidently, and almost never actually tested.

So we tested it.

Over the course of about four weeks, the Return Flights team tracked and booked 50 round-trip itineraries across a range of popular US routes — domestic and international — varying the day of the week, time of day, and how far in advance we searched. We kept the routes consistent, the travel dates fixed, and changed only the booking timing. Here's what we found.

The Setup: How We Ran the Experiment

First, a note on methodology. We focused on ten routes that represent a cross-section of American travel patterns: New York to Los Angeles, Chicago to Miami, Dallas to Denver, Atlanta to Seattle, and Boston to Orlando on the domestic side, plus New York to London, Los Angeles to Cancún, Chicago to Paris, Miami to Mexico City, and Dallas to Cancún internationally.

For each route, we tracked prices every day for four weeks, recording the cheapest available round-trip fare at five specific time windows: early morning (6–8 a.m. ET), midday (12–2 p.m. ET), and late evening (9–11 p.m. ET) on Tuesday, Wednesday, and Sunday — the three days most commonly cited as optimal by travel blogs and airline insiders.

We used a consistent search window (departing roughly six to eight weeks from the search date, returning seven days later), searched in incognito mode, and cross-referenced prices across Google Flights, the airline's own website, and one major OTA. All prices are in USD and reflect the lowest available economy fare including standard taxes.

This isn't a peer-reviewed academic study. But it's a lot more rigorous than "my cousin swears by Tuesdays."

Finding #1: Tuesday Is Real — But Barely

Let's start with the big one. The Tuesday booking myth has been around for decades, originally based on the idea that airlines release fare sales on Monday nights, competitors match them by Tuesday morning, and the window of cheap seats closes by Wednesday. Is any of that still true?

Kind of. Across our domestic routes, Tuesday searches did return the lowest average fares — but only by about 3.2% compared to the weekly average. On some routes, that amounted to less than $10 on a $300 round trip. Statistically meaningful? Marginally. Worth rearranging your schedule? Probably not.

More interesting: the time on Tuesday mattered more than the day itself. Early morning searches (before 8 a.m. ET) consistently returned fares that were 4–6% lower than the same Tuesday afternoon searches. Our theory is that fare algorithms reset overnight and haven't yet adjusted upward in response to morning demand signals. By noon, prices had often ticked back up.

Finding #2: Thursday Performed Worse Than Expected

Thursday gets mentioned in some booking guides as a secondary sweet spot. Our data didn't support that. On domestic routes, Thursday was actually the second-worst day to search in our sample — trailing only Friday, which was consistently the most expensive day across nearly every route we tracked.

The intuition here makes sense when you think about it. Thursday is when leisure travelers start finalizing weekend plans, which drives up short-term demand and signals to pricing algorithms that seats are moving. Airlines respond accordingly.

For international routes, Thursday performed slightly better relative to other days, but still came in below Tuesday and Wednesday in terms of average fares found.

Finding #3: Sunday Has Been Underrated

This was the most surprising result in our experiment. Sunday evening searches — specifically between 8 and 10 p.m. ET — returned some of the lowest fares we saw, particularly on international routes. On three of our five international pairings, the cheapest fare we found over the entire four-week period appeared on a Sunday evening.

Why? A few possible explanations. Business travelers (who typically book during weekday business hours) are less active on Sunday evenings. Airlines may be running weekend promotions that haven't yet been matched or pulled. And some algorithmic pricing models appear to deprioritize revenue maximization during low-traffic browsing windows.

We're not ready to declare Sunday the new Tuesday. But based on our data, it deserves a lot more attention than it gets.

Finding #4: The Advance Booking Window Is More Important Than the Day

Here's the finding that probably matters most. Across all 50 bookings, the single factor most correlated with lower fares wasn't the day of the week or the time of day — it was how far in advance we searched.

For domestic routes, the sweet spot in our data was 5 to 7 weeks out. Fares searched within two weeks of departure were, on average, 34% higher than fares found at the five-to-seven-week mark. Beyond eight weeks, prices didn't drop significantly further — and in some cases, very early searches (12+ weeks out) returned higher fares than mid-range searches, likely because sale inventory hadn't been released yet.

For international routes, the optimal window shifted earlier: 8 to 12 weeks out consistently yielded the best prices in our sample. Beyond that, fares were either comparable or slightly higher. Within four weeks of an international departure, prices were dramatically elevated — sometimes double the baseline.

If you take nothing else from this experiment, take this: booking at the right time in advance will save you more money than booking on the right day of the week.

Finding #5: The Return Leg Has Its Own Pricing Logic

Since we're Return Flights and both legs of the journey matter to us, we paid specific attention to whether the return portion of a round trip was priced differently depending on booking day.

The answer: sometimes, yes. On about 30% of our searches, we found that the price difference between the cheapest and most expensive booking day was more pronounced on the return leg than the outbound. This aligns with how some airlines price return inventory — particularly on popular leisure routes where the return flight (think: Sunday evening from Orlando back to New York) is in higher demand than the outbound.

If your return leg falls on a high-demand travel day, that's where the most pricing volatility lives. Booking early matters even more for those segments.

What This Means for Your Next Booking

So what's the practical takeaway from all of this?

• Don't obsess over Tuesday. It's slightly better than most days, but the margin is small. Early Tuesday morning is better than Tuesday afternoon, if you're going to bother.
• Avoid Friday searches. This was consistently the worst day in our data.
• Give Sunday evenings a shot — especially for international routes.
• Book domestic trips 5–7 weeks out. For international, aim for 8–12 weeks.
• Watch the return leg closely if you're flying back on a peak travel day.

The myths aren't entirely wrong — they're just oversimplified. The truth, as usual, is a little more nuanced. And now you have actual data to back it up.