You may have heard that the best day to buy an airline ticket is a Tuesday.

Other things you may have heard: Polaroid cameras now let you see photographs shortly after you take them, and bloodletting is no longer an accepted cure for fever.

In other words, it’s outdated information. The standard explanation for the Tuesday theory was that airlines release their bargains early in the week and competitors scramble to match them. But even if there’s still some truth to that, other variables have complicated things.

There are plenty of companies out there offering reports and tools to help you navigate this and other airfare decisions — Google’s Explore Flights engine and Kayak’s price trend feature among them. But a few months ago, some smart people at a company called Hopper, whose primary business is aggregating blog posts for travelers, started releasing intriguing reports about how to lower your travel costs. The reports (available at, by signing up for their mailing list or following their chief data scientist on Twitter, @patricksurry) are coming with a frequency, transparency and detail I haven’t seen in other reports that try to answer similar questions — and I’ve looked.

And while static reports provide only broad conclusions, Hopper also provides customizable tools that are as powerful as they are simple to use. Hopper’s detail and customizability mean more specificity, whether you know exactly where you’re flying or still haven’t decided. And they’re doing it with a huge amount of data, about a billion price points delivered to them every day. After taking the reports and tools for a long spin, I came up with some conclusions; here are a few of the most useful.

When to Book and When to Fly

The overall take on the best day to book tickets turns out to be somewhat underwhelming, if you look at the country as a whole. Hopper’s data shows it’s actually Thursday, but don’t expect that fact to save you much money. Reserve a domestic flight on Thursday and you’ll spend, on average, $10 less than if you reserve on Saturday, the worst day to book domestic flights. With international flights, you’ll save, on average, $25 over Sunday, the worst day to book flights abroad. (Those are “maximum averages” that assume you would have booked on the worst day and are now booking on the best.)

But even before we get to those custom tools, some useful tips emerge: For the vast majority of routes, weekends are the worst time to book, and for about two-thirds of routes, Wednesday or Thursday is the best day. So avoid booking on weekends and try midweek; for the average American flier, those savings will add up in the long run.

Hopper’s reports also show that the day of the week you depart and the day you return matter more than the day you book. For domestic flights, leaving Wednesday (the best day) will save you $40 on average over a Sunday departure (the worst day); returning Tuesday will save you $45 over returning Friday. For international flights, Wednesdays are the best day to both leave and return.

Again, that’s on average. But of course, you’re neither an average traveler nor are you taking an “average” flight. You’re going from Chicago to Boston for a cousin’s graduation in two weeks, or planning a family trip from San Diego to New Zealand for September.

That’s where Hopper’s “Origin-Destination” reports — available at — come in. Pop in any route, and get a customized report with the cheapest day to book, the cheapest day to fly, average costs and much more, including specific numbers on how much you can expect to save.

Take a very popular route, like J.F.K. to Los Angeles International Airport, for which Hopper’s report uses 57 million fares quoted in the last month. Turns out you’d be crazy to book Thursday through Monday, since, according to the graph I got, you would save an average of $45 or so by booking on Wednesday (Tuesday is somewhere in the middle). You’ll also find that returning Tuesday will save you an average of $35 over returning Thursday through Sunday.

And you needn’t limit yourself to the busy routes. I ran Dallas/Fort Worth to Beijing, and found that Tuesdays are magic: For the average passenger, departing on Tuesday is $200 cheaper than departing Friday through Monday. Returning Tuesday is also $100 to $200 cheaper than any other day.

Where to Fly

It’s not all about when you fly, but where. One of Hopper’s most interesting reports tackles flying to Europe this summer. They produced a list comparing the most-searched European destinations from each of four cities — New York, Los Angeles, Boston and Chicago — with the cheapest destinations and came to some intriguing conclusions.

Not surprisingly, London, Paris and Rome are at or near the top of the popularity list for all four cities. But the cheapest destinations from each of those cities varied widely. For New York, it’s Bergen in Norway and Oslo and Copenhagen; for Chicago, it’s Warsaw and Stuttgart and Düsseldorf in Germany; for Los Angeles it’s Copenhagen, Stockholm and Moscow; and for Boston it’s Lisbon, Dublin and Istanbul.

That’s good news for Chicago’s big Polish population and Boston’s Irish community, not to mention any pickled herring fans in New York City — but not just for them. The price differentials are significantly higher, in some cases, than adding the cost of an intra-European flight. In other words, say you live in Boston and want to take your family of four to Paris. The average flight costs $1,089, whereas the average flight to Lisbon is $677. Find a cheap flight from Lisbon to Paris — they go for as little as $150 — and voilà, you’ve got a Lisbon-Paris vacation for less than going to Paris alone.

(Note that this doesn’t mean it’s a good idea to skip Lisbon by booking a connecting flight directly to Paris. If you book two flights separately and miss the connection, the airlines have no responsibility, and you’ll be on your own getting to Paris.)

Hopper’s interactive tools also work well for choosing a destination. They take your home airport and spit out a world map with average prices by city, so you can also find, say, the cheapest destination in South Asia from Cincinnati. (It’s Colombo, Sri Lanka.)

There are some final caveats to the Hopper reports. As is always the case with data crunching, they’ve done some adjusting: For example, the “average” prices are actually the average for the cheapest 10 percent of results. That makes sense, since most people ignore the least useful search results — say, an Air India flight from New York to Washington, with a stopover in Mumbai, for $6,500. And of course, their conclusions are based on past data. If thousands of Texans read this and go online next Friday to book flights to Beijing returning on a Tuesday, prices might very well rise.

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