If sitting is the new smoking, then flying in economy must be the equivalent of a pack a day.

　　Remaining seated for extended periods, whether you’re working at a desk or road-tripping hundreds of miles, causes blood to pool in your legs. Sitting on a plane exacerbates this, because air-pressure changes in the cabin lowers the oxygenation of your blood, which can adversely affect circulation, causing veins (and your legs) to swell. In some alarming cases, it can even lead to deep vein thrombosis (DVT), a rare yet serious condition in which a blood clot forms in your leg and travels to your lungs; this could result in a pulmonary embolism.

　　Compression socks for flying can help. Tightest near the ankle, and still pretty snug at the top of your calf, they’re designed to gently squeeze your lower legs to stimulate blood and lymphatic fluid from your feet to your heart, explains Andrew Jagim, director of sports-medicine research at the Mayo Clinic.

　　Before you balk at paying upward of $20 for a pair of tight socks, consider how economical this purchase is compared with a business-class seat that lets you fully recline. The lie-flat option is often 100 times more expensive, which is why I’ve come to rely on compression socks—what I call the poor man’s upgrade.

　　How Compression Socks Came to Be Viewed as Essential for Travel

　　Conrad Jobst, a German engineer who lived in Ohio and suffered from varicose veins, is credited with inventing modern compression socks around 1950. His therapeutic designs helped alleviate symptoms associated with poor leg circulation, post-surgery swelling, and DVT, among others. Jobst Stockings are still sold today.

　　That decade, experts began to recognize that prolonged periods of immobility during long-distance travel, particularly by car or train, could cause blood clots to form and started using the term “traveler’s thrombosis.” In 1954, American surgeon John Homans reported cases of people who had experienced venous thrombosis after long-distance flights.

　　The media and general public were alerted to the connection between flying and DVT in 1974, when then U.S. president Richard Nixon developed a blood clot while flying during a diplomatic visit overseas. Complications required hospitalization and prevented him from being able to attend the Watergate trials.

　　A few years later, two British researchers studying the risks of DVT on flights coined the term “economy class syndrome”— a misnomer, as DVT can occur in any class of travel, but highly influential in drawing attention to the risks of air-travel-related DVT, says Bob Bacheler, managing director of the medical-transport service Flying Angels. “Having more space to stretch your legs or lie flat is better than being cramped in economy, but you still need to make the effort to move,” he says.

　　Who Should Wear Compression Socks, and When

　　According to the Centers for Disease Control and Prevention, anyone traveling four-plus hours—be it by air, car, bus, or train—can be at risk for blood clots. Occurrences of a blood clot are between 1.5 and 4 times more likely on a long-haul flight (four hours or more), according to a review of trials that was updated in 2021. That said, most people who develop travel-associated blood clots are generally those with one or more health risks; for example, they’re over 40, obese, pregnant, or recovering from a recent surgery.

　　Jagim says that wearing compression socks on any flight longer than an hour can yield benefits, like minimizing lower-leg and ankle swelling. Bacheler, who frequently serves as a flight nurse on flights of 12 to 24 hours, says he always wears compression socks. Of the two dozen flight attendants I polled during my own recent travels, all but one said they wear them, even on flights as short as one hour.

　　But these special socks aren’t a magic fix. Whether you’re sprawled out in the spacious Qsuites of Qatar Airways or packed like a sardine into economy on Frontier or Spirit (tied for the least leg room at 28 inches), it’s important to get up and walk to keep the body’s interstitial fluid—the stuff between our blood vessels and cells—moving. The CDC recommends getting up once every two to three hours. Jacob Erickson, a sports-medicine specialist at the Mayo Clinic, says that even flexing your calf muscles and moving your feet and ankles around while sitting can help blood flow.

　　And don’t forgo hydration. Kill two birds with one stone by getting up, walking down the main aisle, and asking a flight attendant for water. “Staying hydrated complements the effects of compression socks by ensuring your blood remains fluid and your body maintains overall balance,” says Bacheler.

　　How to Shop for the Right Compression Socks

　　As a travel writer, I fly a lot—most recently, 13 flights in three weeks—and have tested dozens of compression socks to determine which are best at preventing my legs from inflating like balloons. The most important consideration, according to Bacheler, is a good fit. Too tight and they’ll cut off circulation; too loose and they’ll fail to compress sufficiently. Most medical-supply stores will have a variety you can try.

　　Understanding Mm Hg Every compression sock offers information about mm Hg on its packaging, so you should know what it means. The measurement stands for millimeters of mercury (what we use to gauge blood pressure), and it reflects the amount of pressure the socks provide.

　　Most brands tend to use the following general ranges of mm HG. Finding the right fit might take some trial and error, but go by what feels best to you.

　　8 to 15 mm Hg: Light compression that can relieve aches and minor swelling from prolonged sitting or standing; considered a loose fit.

　　15 to 20 mm Hg: Mild compression suitable for everyday use.

　　20 to 30 mm Hg: Moderate compression used in medical-grade socks; a very snug fit.

　　My Travel-Socks Hack On a recent trip from Madagascar to Denver (four legs, 31 total hours in the air), I paired my mild compression socks with Band-Aid-size Firefly electrical-stimulation devices (from $48), for the marathon 15-hour leg from Doha, Qatar, to Seattle. The devices send out tiny pulses that stimulate the peroneal nerve in the leg to increase blood flow.

　　The winning combination prevented swelling and left my legs feeling like Id never left the ground. If you check out the brand’s website, you’ll see that this is something used by hundreds of sports teams that travel on the regular.

　　My Favorite Compression Socks for Flying 2XU

　　Price: $45

　　Compression level: 15 to 20 mm Hg

　　I’ve long worn 2XU flight-compression tights to help recover from long runs or tough workouts, so I decided to try the brand’s flight-compression socks on that recent 15-hour leg, and I’m hooked! Each pair is assessed on Salzmann testing apparatus—the most technically accurate device for compression measurement in fabrics—to ensure graduated squeezing. A vented toe panel provided breathability, and they were easy to pull on and off. One downside is that they lose their compression characteristics after a few machine washes, so hand-wash yours.

　　Buy 2XU Flight Compression Socks

　　Bombas Everyday

　　Price: From $28

　　Compression level: 15 to 20 mm Hg

　　Many compression socks pull up to just the base of the knee. But if you have sensitive knees, you may find the squeeze at that point irritating or even painful. Bombas Everyday socks are a nice alternative—they’re designed to hit a few inches below the knee yet still stay snugly in place. I tend to get cold on flights, and was pleased to note that the Everyday’s cotton blend was warmer than others I’ve tried. I give the brand bonus points for its colorways, which range from neutral (black, gray) to colorful (plum, ocean).

　　Buy Bombas Everyday Socks

　　Comrad CloudCotton

　　Price: $32

　　Compression level: 15 to 20 mm Hg

　　Comfy enough to wear all day long, these socks are crafted from supersoft combed cotton and tree fibers, and they almost feel like slippers on your feet. I appreciate the extra toe and heel cushioning, which helps with shock absorption. And the moisture-wicking, odor-fighting fabric means you can kick your shoes off mid-flight, worry-free. I couldn’t decide whether to buy a small or medium and wrongly chose the latter, but the Comrad guarantee allowed me to exchange for a different size for free (or return them for a refund) within 30 days of purchase.

　　Buy Comrad CloudCotton Socks

　　Levsox

　　Price: From $25 for two pairs

　　Compression level: 20 to 30 mm Hg

　　Thanks to their breathable fabric, Levsox don’t feel like they’re strangling your legs, but they still deliver the firmer fit I prefer. Their extra arch support is akin to getting a massage while you walk. If you like socks with personality, you’ll love the options: stripes, animal patterns, and psychedelic prints. Levsox also makes a model suited for wide calves.

　　Buy Levsox

　　Sigvaris Motion High Tech Calf Highs

　　Price: $68

　　Compression level: 20 to 30 mm Hg

　　Bacheler and three flight attendants I spoke with all swear by Sigvaris compression stockings. Most medical-grade models resemble your grandma’s hosiery, but these particular knee-highs look like sporty socks, and they pop in bold hues like lime green and steel blue. They apply more compression in the calf area than other socks on this list, which kept my legs feeling energized when I deplaned and had to race to my next flight.

　　Buy Sigvaris Motion High Tech Socks

　　Jen Murphy credits compression socks for allowing her to fly ten-plus hours and then go run five miles without aches or pains.