Anonymous wrote:CARES doesn't work for the majority of kids who are technically within its weight limits, because it can't prevent smaller/lighter kids (less than about 40 lbs) from sliding out under the airline seatbelt. So if your kid is between 40 lbs and the CARES limit of 44, you're good to go.
Otherwise, take the car seat on the plane. It will be more familiar to him and there are times when you just plain have to have the kid harnessed down, period.
This means you're doing it wrong--you're basically saying that any toddler can get out of just a lap belt, no matter how tight. It takes practice, but the key to installing CARES is to tighten the lap belt first, before you adjust anything else. If you try to do the shoulder straps first, you end up pulling the lap belt up, creating a gap. LAP BELT FIRST.
I've been using CARES since my child was 20 months.