Traveling by plane with kids is stressful - there's no way around it. 
You're all trapped in a little metal tube for hours on end with hundreds
 of strangers and no way to escape. There are a few major differences 
between traveling by air and traveling by car with kids and by far, the  
most important one is that traveling by car your kids can only drive 
YOU crazy - as opposed to the entire plane full of passengers. The best 
way to ensure that your family has a successful flight is to realize 
that your number one job is to entertain the kids, which means you 
probably won't have time to read much of that novel or magazine or trade
 journal, or catch up on movies. With that in mind you must know that 
most of these suggestions will involve you to one degree or another.
1. Airplane travel is a time to make a few key adjustments to your family rules re: behavior.
 When we fly, we get more strict about our children adhering to our 
rules for public behavior (things that affect others) i.e. use your 
indoor voice, no throwing things, no roughhousing, try to keep the 
nose-picking to a minimum. . . you get the idea. On the other hand, we 
relax some of our other rules for this special time, so there are no 
limits on media use, they are allowed to eat more 'junk food' or treats,
 we're more tolerant of special requests, and we are much more likely to
 give in to whiny requests than we otherwise would be. No one wins by 
trying to make a point to a three-year-old 5 hours into a 10-hour 
flight. Once we were stuck waiting out a lengthy delay in the departure 
lounge at the beginning of an overseas flight. We bought our little ones
 a treat of some ice-cream bonbons, and at the end of the box our son 
started to get into a first class freak-out that he hadn't gotten his 
fair share. Normally he would've been out of luck, but in that special 
case we just went and bought another box.
2. Research your destination and layover airports ahead of time -
 our local airport (SeaTac - SEA in Seattle) has an indoor 
playground where the kids can safely run around and blow off steam, with
 large family bathrooms located right beside it. Chicago O'Hare (ORD), 
San Francisco (SFO), Boston (BOS), Dallas-Fort Worth (DFW)
 and Portland (PDX) all have great playgrounds as well - some more than 
one. Other airports offer special tours for kids, airport based exhibits
 from the area's museums and areas with kid friendly food vendors. It 
pays to take a few minutes before your trip to see what the airports 
you're traveling through have to offer, and make a note of where the 
attractions are, because they're sometimes tucked away in a spot you 
might not pass otherwise.
 
3. Read books and talk about air travel with your kids ahead of time - my 
kids really like '
Going on a Plane' and '
A Day at the Airport'.
 These are especially 
useful to get your kids used to some of the more unusual parts of plane 
travel, especially the security screening and flight attendant 
interaction. Talk with them about what the airport and the flight will 
be like, including how long it will be and what will happen - will you 
eat dinner, then sleep and wake up and eat breakfast? Maybe just eat 
lunch and then have a nap? Gently reinforce your expectations in the 
days or weeks before the trip so that they're not surprised during the 
actual flight.
4. Bring spare clothes; more than you normally would for a day trip.
 Pro-tip - pack each change in its own gallon ziplock bag (you can 
squish the 
extra air out to conserve space). If you need the spare on the trip, its
 likely you'll be glad to have the empty bag to contain the dirty 
clothes.  This includes for yourself - we always bring at a minimum an 
extra shirt for each adult too since there's a good chance if your child
 gets grossly dirty you might be too.
5. Think about strategies to alleviate ear pain on takeoff and landing.
 The most important thing is to keep your child swallowing periodically 
to equalize the pressure in their ears. Juice boxes, milk boxes, gum, or
 lollypops can all help. We haven't had any problems going through 
airport security taking two small juice boxes per kid per flight inside 
the US; I just bag them in a ziplock bag and send them through the x-ray
 scanner along with the toiletries. Consider packing enough for the 
return flight in your checked luggage (especially if you are traveling 
to an unfamiliar area that might not have the brands/flavors your child 
usually has - we drink/eat whatever is available at our destination 
during our trip, but again, the flight is not really the time to have a 
standoff about how the local beverages taste). If you don't want to deal
 with beverages you can offer a lollypop at takeoff and landing - that 
can be effective especially if its a kind of special treat for your 
child.
6. Bring lots of snacks and make sure there are more than just sugary treats.
 These days it's rare to get free food on a flight, and snacks serve a 
couple of purposes: 1) they stave off the hungry crankies, 2) they're a 
good distraction, and 3) they can serve as a bribe if necessary. When we
 travel we bring snacks that our kids don't usually get at home - our 
kids especially love to get their hands on handisnacks (with the 
crackers and "cheese" and a little stick for spreading) which they never
 get any other time. Other good snack options are granola bars, cheese 
sticks, crackers or chips and fruit.
7. Introduce your family to the Travel Fairy. The Travel Fairy 
stops by on every trip our family takes, to make sure the kids aren't 
bored and are well behaved. She gives them little gifts and treats, and 
most importantly, everything she gives is wrapped up in wrapping paper. We wrap 
up everything the kids will have on the flight, even things they already
 have (like books for their Tag reader pens, or crayons), even sometimes
 their snacks. We try to dole out Travel Fairy gifts infrequently, and 
make sure that we've saved some for the return flight. 
8. Drawing utensils for writing or coloring. This could be an 
aqua- or magna-doodle for a toddler, or crayons or markers for an older 
child. Square or triangular crayons are useful for littler kids so that 
they don't roll off the tray so easily, and markers whose lids snap on 
the end easily are good for older kids, for the same reason.
9. Electronic learning activity toys make for good distractions. 
We are a 
Leapfrog family, but 
V-Tech also makes nice toys with learning 
activities. Its a good idea to bring along a set of headphones (I like 
these 
noise-limiting headphones for small kids)
 to avoid disturbing those around you, although I've found that using 
toys or electronics with the volume low works since the ambient 
plane/engine noise is so loud.
10. Bring along a few new thin paperback books to read to your children.
 Most kids love story-time, and new books will hold their attention 
longer than ones they've read a lot. Of course, if there are a few books
 that your child could read over and over every day, by all means bring 
those!
11. Felt boards for storytelling and imaginative play. These are lightweight and can be either purchased or easily made. I put cardboard backing on the 
boards I made, but you could go without and have an even lighter and smaller activity.
12. Pipe cleaners or Wiki Sticks make for crafty, quiet entertainment.
 For very young children you'll need to be the one crafting them into 
shapes that can then be used for imaginative play - older kids can work 
more independently but might still need some help to see how sticks can 
be joined together. Our kids have made (or played with) horses, dogs and
 other animals, flower bouquets, crowns, jewelery and shapes.
13. There are tons of blog posts around that give ideas for toddler busy boxes/bags
 - peruse them to choose ideas that might entertain your little ones 
while still being quiet, light and easy to pack. I especially liked this
 
one, this 
one, and this
 one.
14. Sticker books with reusable stickers are lightweight and easy to pack - you could get one that relates to your destination or one more
 travel-centric (what you can see at the airport).
15. Sticking with the same sticker theme (see what I did there?) -
 dollar stores and the $1 area of Target often have sticker packs with 
either seasonal themes or others like construction vehicles or farm 
animals that your kids can use to make their own scenes. I like to 
prompt my younger child by drawing a simple scene on a piece of paper 
than he can then add stickers to, like drawing a town layout with a few 
roads where he can add car and truck stickers.
16. iPad, iPod, iPhone or the like can be a lifesaver - load it 
up with games and videos. We use two iPod Touches which belong to my 
husband and me but for the duration of travel are claimed by our kids. 
For our last trip we also brought 
these external batteries,
 which helped for a long flight. I made sure that each iPod had 
different games and videos so that the kids could trade and have more 
things to do and watch.
17. Printable activities of your child's favorite TV shows/characters.
 Nickelodeon, PBS, Sprout and Disney all have websites where you can 
download and print activity pages. I usually put them into a report 
folder to keep them contained and organized. I like to do this instead 
of bringing one coloring book per kid because they can have more of a 
variety that way.
18. Travel journals with fun activities about your trip. I make 
travel journals
 for my kids before long trips using cheap blank notebooks and 
embellishing them with route maps, travel games and printed out puzzles 
and mazes. Then the kids use them throughout the trip as their notepad /
 coloring paper and afterwards to add in stickers and postcards and 
other little paper souvenirs from the trip.
19. Quiet card games to play - a regular deck of cards works for 
older kids, and younger kids would love to play with a Go Fish or Old 
Maid deck, or a small set of memory match cards. You can even make your 
own version of Memory if you like - either printing a set off the 
internet or drawing your own pictures. You can also make variations on 
Memory than can be great learning tools, like sight word matching or 
matching numbers with a picture of that many objects.
20. Word games and finger plays. It helps to have an arsenal of 
word games and other little activities ready that don't need anything 
but yourselves to play. Some of our favorites are "I Spy" ("I spy with 
my little eye something brown" and then people take turns guessing what 
it is), the "Story Game" (where each member of the family adds onto a 
story sentence by sentence and the last player has to add their ending 
and then recite the whole story) and the "Alphabet Game" (where each 
member of the family thinks of a word that starts with each letter of 
the alphabet). Another game that works well at the airport during layovers or before or after your flight is a variation of I Spy where you ask each child to spot a different thing that is not immediately visible but that might be seen readily (Can you find a blue suitcase? Can you spot a pet in a carrier? Can you see a mom with a baby?).
21. Route maps. I like to draw 
simple route maps that help my children visualize where we're going and how long it will take us. For airplane travel I divide the trip up into time segments and let them color in the segments as we go along for a visual indicator of "when will we get there?". 
22. Coins can be fun. Your spare change can be used as entertainment as well. Let your children sort the coins into groups by size and/or color (of course watch toddlers carefully since coins are a choking hazard!), or use them to make rubbings by putting them under a piece of paper and rubbing crayon or pencil lightly over the top. Older kids can practice making change in a variety of different ways or practice sleight-of-hand tricks, making a quarter appear or disappear.
This post was adapted from a post on my lifestyle, cooking and craft blog MakeSomethingDaily.com