M.B.
The britax frontier. It has the ability to hold a child in the 5 point harness until 80 pounds, then converts to a seat belt booster until 110 pounds with back support. It is regulated for airplanes, as we travel throughout the year. It is larger and heavier, although a plus in my mind. My daughter is 5 and in the 95percentile in weight and off the chart in height, yer she is comfortable and not squished into this seat. Hope this helps.