Here are nine tips that I have learned from traveling with my little Mia on airplanes over the years - this post is specifically about traveling with a 3-year-old.
1. Layers. Layers. Layers. (Use layers for your child's clothing).
Use layers for your child's clothing to make sure they stay at a comfortable temperature. Airplanes have very unpredictable temperatures when on board - and trust me from experience that children are NOT happy when they are hot (I personally get very cranky when I am hot too).
My advice: Put your child in a t-shirt, and bring a light jacket that they can wear over the t-shirt.
2. Use a scarf as a blanket.
A blanket is always good to bring, but one thing that I like to do in place of a blanket is to wear a scarf around my neck and then use the scarf for their blanket (to save space in the diaper bag).
3. Surprise your child with a toy airplane.
If your child is afraid of airplanes or unfamiliar with airplanes, then going on the plane can become a lot more fun if you surprise them with them very own toy plane.
TIP: A lot of airports sell toy airplanes in the airport stores in the terminals.
4. Do your "Ear Check" due diligence.
Ask your doctor what your options are to help relieve your child's ear discomfort during the ascent and descent in the air.
5. Consider using the Best Travel Potty ever...
The Kalencom 2-in-1 Potette Plus Travel Potty has saved my sanity so many times while traveling with my potty-training toddler, and we still use it for traveling with our Preschooler. It is amazing. I never thought I'd be so passionate about a toilet seat in my life. I would post pictures to show you how we use it, but that would be gross and my child would never forgive me.
6. Bring Wet Wipes.
....because airplanes are dirty.
7. Apps for Kids
Download age-appropriate apps for your child on your cell phone. My daughter's two favorite apps are "Make it Pop" and "Peek-a-Boo Zoo."
8. Find the "Family Restroom" at your airport.
Family restrooms are SO much better than the regular restrooms at airports - see the photo below for an example of the Family Restroom at LAX airport - this airport has child-sized toilets and child-sized sinks, which made me extremely happy.
9. Look for pull-down step stools in airport bathrooms.
Some airports, including LAX, have stools that you can pull-down from right underneath the sink, which is fabulous for when your child needs to wash their hands (with this stool, you don't have awkwardly lift your child up to the sink - it's amazing).