Any parent of multiples will tell you: Traveling with twin babies can be challenging, especially if you're flying. But it can also be incredibly rewarding. Whether you're visiting Grandma and Grandpa or jetting off to a new vacation destination, you're broadening their horizons.

These tips for flying and traveling with twins can help the trip go more smoothly.

Understand the airline rules and regulations for children

The rules for flying with babies and traveling by air with toddlers vary by airline, so be sure to check your carrier's guidelines before you book a trip. Here's what you can expect on most U.S. flights:

A baby under the age of 2 can sit on an adult lap without a ticket

Each baby needs to sit in one adult's lap — so if you're traveling alone with two babies, you'll need to buy a second seat for one baby. While you won't have to pay for a full ticket for your lap baby on most national flights, the airline will require you to notify them of the baby upon booking and charge you taxes and possibly a service fee.

For international flights, most airlines require you to buy a full ticket, even if your baby is sitting on your lap.

You may not be able to travel alone with twins

U.S. carriers — such as Delta and JetBlue — allow up to two babies under the age of 2 per adult. But some airlines may require that each baby travels with one adult, so be sure to check the rules before booking.

Lap babies may not get their own carry-ons

Some airlines allow separate carry-ons for babies without a reserved seat, while others don't.

You may have to split up

Some carriers allow only one lap baby per row on the plane, so you may need to sit separately from your traveling partner.

Bring an FAA-approved car seat

If you book a seat for one or both of your babies, it usually comes at a discounted rate — but you'll need to bring a FAA-approved car seat. Many but not all car seats are FAA-approved; check the user's manual for the following text: "This restraint is certified for use in motor vehicles and aircraft."

Each baby needs paperwork

Even if you don't buy a seat for your babies, they each need paperwork to board the plane. This includes a birth certificate for babies under 2, a medical release from a doctor for newborns (usually under 7 to 14 days old) and a passport (and visa, if necessary), if you're traveling internationally.

Be a super planner

How will you get from the airport to your destination? What's the best route to take? Will you need cash on hand to pay a driver or tip an attendant? A little planning in advance can go a long way to minimize any last-minute scrambles and the stress that can result.

Pack smart

Chances are that you already have all your babies' must-haves tucked into their diaper bag. After all, you're likely out and about with your twins often.

But there are a few other things you'll want to add to a carry-on for a trip. They'll not only come in handy, but they'll also keep you prepared should the airline lose your luggage (yes, it can happen!). If you need to pay for an extra bag to port all of your stuff, it may be worth it for peace of mind. Here's what you should include:

Food and feeding gear

When you're traveling, it's even more important to keep your twins well-fed. So unless you'll be breastfeeding, be sure to bring your breast pump (or formula) and extra bottles.

You can bring pumped milk or prepared formula "in reasonable amounts" on board, but you'll need to present it to a Transportation Security Administration (TSA) officer at the security check-in.

If your kids have graduated to solids, bring more age-appropriate snacks for toddlers, like whole grain crackers with peanut butter, whole grain cereal, all-natural fruit leather and graham crackers, than you think you'll need.

Diapers and wipes

In addition to plenty of extra diaperes, you'll want more than enough wipes for both diaper changes and feeding messes.

An extra change of clothing for each baby

Diaper blowouts can happen when you least expect them. So plan accordingly. Pack an entire outfit for each baby, including a spare pair of socks and shoes.

Plenty of toys

Your twins' favorite toys, plush animals, books and games might take up a lot of extra space, but it's space well-used. Kids get antsy fast, so you'll want lots of distractions to make the time pass more quickly for everyone.

All those important documents

Make sure your tickets, passports or other IDs are all in the same easy-to-reach, separate pocket in your purse or diaper bag. The last thing you want to be doing is sifting through toys and diapers when you need them.

Skip packing nonessentials

While you may be looking forward to digging into that 500-page novel that you've been wanting to read upon takeoff, chances are it will remain unopened in your bag. You'll be too busy taking care of your little ones (and if they do fall asleep, catching up on some nap time yourself!).

Make your load lighter and consider leaving out extras you really won't need. Stick to your essentials — medicine, keys, wallet — instead.

Leave yourself lots of time

Babies need to be fed. They need to be changed. Sometimes there are unexpected delays at check-in.

Make it your mission to arrive well in advance of your departure. That way, if things come up (and when don't they with children in tow?), you'll be able to take a deep breath, manage them and still get to your flight on time.

Divvy up the duties

If you're traveling with a partner, one of you can get dropped off at the terminal with the kids while the other parks the car and brings in the baggage. When you get to the boarding gate, one of you can take the carry-on luggage while the other cares for the kids. Divvying up the duties can make things simpler at every step of the way.

Traveling alone? That's okay too. Just be extra prepared. Also, ask around to see if someone could help you. Even if a friend can travel to the airport with you and bring your bags to security at check-in or assist you upon arrival, you'll find the extra set of hands can give you the freedom to turn to other responsibilities.  

Let your kids play before boarding 

Airports can be full of open areas (and some even have playrooms!). Take advantage of those spaces before you get onto the plane and let toddlers or older kids run around and use up any excess energy. The more tuckered out they are, the more relaxing the flight will be for you.

Bring travel-friendly strollers

Some airlines have a stroller weight limit, so opt for lightweight, travel-friendly strollers or umbrella strollers, which fold up and are easier to move.

Don't check your strollers until you board

Before you board the plane, a stroller can serve as a high chair or as a safe place for one child if your hands are full with the other. Airlines will usually check strollers at the gate right before you get on the plane and bring them to you when you deplane.

Ask for — and accept — help

Many passengers and crew are more than happy to lend a hand carrying baggage or even join in a game of peekaboo to distract a fussy baby. So if you see someone who looks like they're willing to help, or if you're in a real bind and you simply need a hand, don't be afraid to come right out and ask for it.

Be flexible with your rules

An extra treat or screen time while you're flying is worth the hassle it might save you if you usually steadfastly stick to your rules. So if you need to offer up more snacks to toddlers or let your little ones tune into a second episode of a favorite cartoon on an iPad to keep them happy, do it without the guilt.

Stay focused, even if both babies start crying or need to eat

If one baby starts crying or gets hungry, the other is often sure to follow suit. If there are two of you, it's easier to simultaneously soothe or feed. But if you're traveling alone, that's not possible.

So start with one baby and focus all of your energy on soothing him. Once you've got the first baby calmed, move onto the second baby. If it takes longer than expected, take a deep breath. Remind yourself: You're in a tight spot that any parent would have a tough time navigating.

If you're traveling with twins in a train or car, adjust accordingly

Not every getaway will mean traveling with your twins by airplane. If you're going on a road or train trip, the planning and preparations you need to make ahead of time can differ.

In addition to packing smart and mapping out your route before leaving, for example, be sure to plan for more pit stops than usual when you're driving with your little ones. You'll need to feed babies about every two to three hours. If your twins are being potty-trained, you'll want to make frequent bathroom breaks to avoid accidents. And you'll never want to take either baby out of their car seats while the car is moving. If there's a meltdown or a spit-up accident, you'll need to pull over to the side of the road.

Train trips can in some ways be easier than those on a plane, but you can still take some steps to make the journey go more smoothly. Find out if you can be seated near a bathroom with a changing table or a dining car where there will be more space to spread out.

Some seating configurations are also family-friendly so you and your partner can face one another, which makes trading off with twins much more manageable. If you can coordinate your travel around naptime, your babies may even sleep on board, which means everyone will be refreshed upon arrival.