If you have an active child over 2, but you don't feel like lugging that car seat along for the ride, the CARES Harness is a good alternative for those long, or short flights.
The harness attaches to the belt that's already there in minutes and weighs about a pound. Kids will feel like they're in their regular car seat with the harness so it'll be familiar to them.
Find out more, including where to purchase the harness here.
Before & After: Emily Henderson Transforms a Senior's Studio Space
Monica & Austin's Charming Bungalow
Good Food to Share 
The Big Book of Small, Cool Spaces 
Apartment Therapy Presents 
The Eight-Step Home Cure 
White Enamel Four-P...
How to Make Easy 3-Ingredient Energy Bars at Home
True Greek Recipe: Paximadi Bread Salad with Tomatoes, Feta and Capers
We have been using these since our twins turned one and according to their own literature you do not need to wait until your child is 2 years-old. Just over 22lbs.
Yup, it's 22-44 lbs.
Question: Does that red strap go all the way around to the back of the seat? Wouldn't that annoy the person behind you?
It has to go around the whole seat for the harness concept to work, and it goes under the tray. It shouldn't annoy the person behind you at all. Some people don't notice it. Some do and ask about it, but you tell them it's required or something to stop further probing. The strap is NOT in any person's way. Why would it annoy the person?
This harness option is not as safe as a carseat, but families with many kids can't lug so many carseats onto a plane and get them all installed quickly without help.
I have kids so I understand the dilemma of hauling car seats on the plane, I just wondered if that stap around the middle interfered with the tray behind the seat, that's all. It looks like it's smack dab in the middle of where a tray would be.
I think this is a great idea. My husband, who works for an airline, still feels that a carseat is better because not all airplane seats have been tested with this product.
I think people need to look out for the height and weight requirements. My oldest was too tall at 2.5 to use this, but he is still well under the weight. My youngest who is 1 would NEVER sit with this on... the fact that it is not a 5 point is the biggest problem. He would wiggle out... I just know it.