Electa Sam of Kahala was having a drink with Turkish friends on the rooftop bar of the Four Seasons in Istanbul when they noticed something flapping in the air a few floors down. To her embarrassment, Sam realized it was her clothes, which she had hung out to dry on her balcony.

Hand-washable, quick-drying clothes are one of Sam’s travel essentials, allowing her to pack light and live out of two carry-on bags for five weeks.

The good news about flying in summer: You don’t need to take a lot of clothes.

The bad news: Planes will be more packed than ever, with a record 222 million passengers flying on U.S. airlines — a 4.5 percent increase over last summer, according to the industry trade group Airlines for America.

More bad news: Legroom is steadily shrinking. Ten years ago in economy class, seat pitch — the distance between a point on one seat and the same point on the seat in front or behind — measured up to 35 inches. Today some planes have a seat pitch of 28 inches. Ouch.

This makes it harder for airline passengers to exercise or evacuate in an emergency, reports the Advisory Committee for Aviation Consumer Protection, which pressed for government regulation of seat pitch at federal Department of Transportation hearings in April.

Any long flight poses health threats, said Dr. Clayton Chong, an internist and oncologist at the Queen’s Medical Center. Sitting for long periods promotes the development of deep vein thrombosis (DVT), blood clots that can travel to the lungs and cause a pulmonary embolism, a potentially fatal blockage in an artery that feeds the lungs. High-risk factors for DVT include recent surgery, pregnancy, being elderly or obese, or having cancer or cardiovascular disease. But DVT can strike anyone.

"This is a really big, really serious issue. People have to become aware of it," Chong said, explaining that people going on vacation "get all excited, forget to take their meds for high blood pressure, diabetes and heart, don’t exercise on the plane, and end up in the emergency room. And some of them die."

Chong offered five basic tips for a safe and healthy flight:.

» Check with your doctor about what medications you should and shouldn’t take before and during your flight.

» Exercise on the plane. Get up and walk up and down the aisle at least once an hour. While seated, keep legs uncrossed and move feet and ankles.

» Drink 8 ounces of water every hour. Dehydration raises risk of DVT. Do not drink alcohol; it’s dehydrating.

» Wear loose-fitting, nonbinding clothes and shoes.

» Wear compression stockings, which are knit in bands that stimulate circulation. "All adults should start wearing compression stockings on long flights," advised Chong, who wears them himself.

One more risk: air rage. When reclining seat backs come crashing down on knees, tempers can flare.

"We’re now defining air rage as the legroom wars," testified Julie Frederick of the Association of Professional Flight Attendants at the DOT hearing.

How to keep your cool and survive summer airline travel? Read on for more tips from local frequent fliers.

PRE-FLIGHT CHECKLIST

Choose an aisle seat, which, research shows, is associated with lower likelihood of DVT. Before you book your flight, scope out various airline seat maps, plus comfort ratings, at seatguru.com. If possible, limit yourself to two carry-on bags. And that doesn’t mean an overstuffed rollerbag, said Louise Ing, 63, an attorney who lives in Makiki and often travels on business or with her daughter Julia Sitch, 18, who will start college in New York in the fall.

"The challenge when you’re travelling with two women is the balance of not wanting to pay for a checked bag but then you’re going to have to lift that thing by yourself. I’m 5 feet tall and Julia’s 5-2 or 3, so overhead bins are a challenge even with light bags." For this reason, she admits to feeling relieved when flight crews offer to check her LeSportsac soft rollerbag at the gate. "And then you don’t have to pay the checked-bag fee!"

Ing adds that the handle of smaller carry-ons should slip over the rollerbag handle so it can rest on top.

Before entering the security line, Ing tucks her purse into her zippered tote bag, which, like Sam’s tote, can fold up to the size of a cosmetic pouch. That way, the tote can fit in your purse while you promenade through Portland or Paris, to be whipped out when you shop.

Keep onboard essentials, such as a pillow, eye mask, blanket, earbuds, disinfectant wipes, personal-care pouch and portable mobile-device charger in your smaller carry-on so you won’t be parted from them if your bigger bag gets checked. Include an empty, refillable water bottle.

"Lots of airports are starting to add bottle refillers alongside the water fountain," noted Katherine Killebrew, who likes Kleen Kanteens made of lightweight stainless steel.

Regarding essentials, "my main concern is food," said Killebrew, 61, who lives in Wai­alae Nui and is owner/designer of MiNei Designs Hawaii. "Mark (Cunningham, her partner) always says you’re not going to starve in five hours, but it’s also the trip to the airport, the waiting, and I don’t like to eat proc­essed foods."

Their carry-ons contain salads with leftover sliced grilled meat or fish, lots of nuts and gluten-free pretzels.

To reduce water retention and swelling, Sam eliminates salt in her food for two days prior to her flight and while travelling. The 64-year-old retired pharmaceutical sales rep is in Turkey now for a return visit. "I carry unsalted mac nuts or almonds for a snack. No peanuts, as someone may have allergies on the plane," she said.

If you’re flying internationally and want to avoid long lines, invest in Global Entry, advised Ing, who will be going on a European cruise with her daughter and husband. "It’s an $89 annual charge, but you get whisked through international customs and also qualify for domestic precheck."

PACK LESS AND COMPRESS

When Sam departs Hono­lulu, her clothes and things take up only half the space in her rollerbag. The other half is filled with gifts for the friends she’ll be visiting. "So when I give all the gifts away, there’s room to bring stuff back!" Her secret: Pack clothes in vacuum-sealed compressible plastic bags (roll or press them to force the air out, reducing bulk).

Don’t forget double-duty clothes. "I pack — or wear, if it’s a red-eye — jammies I can also wear outside, like pull-on pants and a workout tee," Ing said. "And I wear slippers on the plane because my feet swell, but cute enough to walk in at my destination."

Killebrew wears Tom’s slip-on canvas shoes, which get her through security easily and don’t pinch when her feet swell during the flight.

Kids, of course, change everything.

"I always check everything I can at curbside, all the car seats and luggage, because I need my hands free for my kids," said Katherine Taylor Nordgren, 34, who is Killebrew’s daughter and a stay-at-home mom of four: Jack, 7, Fin, 4, Sunny, 2, and Eve, 1.

The older kids, the two boys, each pack their own backpack and have their own child-size, 12-ounce Kleen Kanteen. Two weeks before the flight, Nordgren and her husband, Joshua, 39, take the children shopping in their Kai­lua neighborhood to select their own snacks, activity and sticker books, crayons, dry-erase boards and, for the oldest, this year, "his own set of earbuds."

"Each kid is really into ‘I have my own what I picked out,’" she said. The parents also help the older children download "tons of audiobooks" from Amazon’s audible.com.

Savvy traveling mom Donica Kane­shiro, 40, assistant features editor of the Hono­lulu Star-Advertiser, said a compact electronics charger is essential when she flies with her sons, Branden, 10, and Adam, 6. She recommends a Lumsing travel charger that works with almost all smartphones and tablets.

Kids or no, arrive at the airport early. Nordgren gets there at least two hours ahead "because I don’t like to feel rushed and tense. … The kids feed off my energy."

Have identification and boarding passes within easy reach in a zip pocket on your purse, smaller carry-on or clothing. "Usually I wear my Ergo baby sling, which has a front pocket that fits my wallet, ID and boarding passes and leaves my hands free for the other kids," Nordgren said. "Things can get out of control really quick if you let something fall into the bottom of your bag."

One must in her diaper bag is a changing pad. She dresses the toddlers in footed onesies so they can go through security without the off-and-on hassle of shoes.

And smile. "My biggest piece of advice to parents is just to stay calm and smile and act like you have it all together," Nordgren said. "That way, other people are more likely to be helpful, hold a child while I’m folding the double stroller to go through the X-ray."

UP IN THE AIR

During the flight, keep your bare minimums in the seat pocket within easy reach. Lip balm and hand lotion in a pouch can feel like lifesavers. So can disinfecting wipes.

"As soon as I sit down, I wipe off both sides of that germ-laden tray table, the armrests and later the bathroom door — everything I touch," said Sam. Kane­shiro covers the tray tables with adhesive place mats, available at drugstores, that can be peeled off.

Ing and Sitch bring their own pillows and blankets — or a lightweight down jacket that can double as a blanket. Ing’s little comfort treats include a lavender sachet or essential oil spritzer and a chocolate bar. Her latest acquisition is an inflatable pillow that pads the entire seat back.

Sitch always takes her trusty hoodie "to protect my head, because the seat backs can be kind of gross," said the college-bound teen. If she doesn’t want to wear it, she spreads the hood over the top of her seat like a slipcover.

Showing kindness and empathy for fellow passengers — including your own family — makes for a smoother ride for all. "When I get on the plane, I always check to make sure there’s a vomit bag in the seat pocket because one of my kids gets motion sick," Nordgren said. "If a child gets sick or throws a toy down the aisle, I’m always gracious to the people around me, thanking them for having us but not apologizing for being us. … I never want the children to feel I’m embarrassed of them."

Advised Sam, "Keep a positive attitude and enjoy your fellow passengers and flight personnel. They may have helpful hints for your new destination!"

Once you get there, peel off those compression stockings and kick up your heels — you’ll have earned it.

TRAVEL MUST-HAVES

1. Padded 40 Blinks sleep mask, $12.95, bucky.com
2. Lug Nap Sac fleece blanket and pillow, $37, lugtravel.com
3. Patagonia down sweater, $229
4. Compression socks: Sockwell Elevation Compression Socks (pictured), $25, Travelsmith.com; Orient Express Argyle Travel Compression Socks, $29.95, herringtoncatalog.com; Futuro Revitalizing Socks, $10.99, futuro-usa.com
5. Havaianas slippers, $20 and up, islandsole.com

PERSONAL CARE

1. Hawaiian Bath & Body Kahala stick in ocean mint, $3.49 at Whole Foods Market
2. Bonny Doon Farm Lavender Spritzer, 2-ounce bottle, $6.75, bonnydoonfarm.com
3. Quies Boules wax-and-cotton earplugs, eight pairs for $5.49, earplugstore.com
4. Wet Ones Antibacterial Wipes, box of 24 for $1.98, walmart.com
5. Filthy Farmgirl Smoochie Stick in coconut lime, $4.29, Whole Foods Market
6. Health Warrior Chia Bars, five bars for $23.50 at healthwarrior.com; also available at health food and variety stores
7. Schiff Knock-Out with melatonin, $14.99, drugstore.com
8. Andalou Naturals 1000 Roses toner, and night and day creams from Essentials Travel Kit, $22.99 ($19.99 June special), Whole Foods Market
9. No-Jet-Lag Homeopathic Jet Lag Prevention herbal supplement, $17.99, Whole Foods Market
10. Honey Girl Organics lip balm with orange oil and vanilla extract, $7.99, Whole Foods Market
11. Lumsing backup travel charger, $19.99, amazon.com
12. Klean Kanteen stainless-steel bottle, from $13.95, kleankanteen.com

REST AND COMFORT

>> Inflatable 1st Class Sleeper by Travelon, $29.95 amazon.com
>> LL Bean Stowaway Down Pillow with water-repelling DownTek and pouch $44.95, llbean.com
>> Bucky millet- and buckwheat-filled neck pillow, $29.95, bucky.com