# Aircraft seats are different from motor vehicle seats, so some auto products work differently and fit differently in them.
# Crash tests have shown that car safety vests and booster seats with shields may not protect a child in an aircraft seat. Therefore, they are not allowed during take-off and landing, even though some have labels saying they are certified for aircraft use.
# Some aircraft seats have backs that fold forward. In a crash, a child in a shield-booster could be crushed against the shield.
# A belt-positioning booster seat that uses a lap and shoulder belt in a car cannot be used. There is no shoulder belt for upper-body restraint. If the booster seat has an internal harness and your child weighs less than 40 pounds, you can use it that way on aircraft. For a heavier child, use the lap belt alone.
Is there a reason you aren't taking your regular car seat? Most children fly better in their "own" seat, since they are familiar with it. I have 4 DDs and have flown with them all since they were 2 weeks old, so I understand it's no fun and sometimes a pain, but is a necessary part of air travel with children. I used a rolling luggage carrier with the seat strapped to it (when DD1 was little, I actually strapped her into the seat and pulled her through the airport that way). Push the stroller with one hand and pull the seat with the other. There are also shoulder bags/straps that can be attached to carry the seat. Having flown more times than I can count and seeing children injured or simply so uncomfortable that they scream for 8 hours, I can easily say that taking your own carseat is worth the hassle for you and those travelling with you.