I have been flying with my daughter since she was about one and we have never used a car seat or booster on the plane, she is 5 now. I was told that the only car seats they allow have to be FAA approved and those are the infant seats. You will probably need it at your destination, but here in Florida kids don't need a booster after 4 years old.
http://faa.custhelp.com/app/answers/detail/a_id/29/sessio...
Does the FAA require children on commercial flights to be in child restraint systems (CRS)?
Published 12/11/2003 03:26 PM | Updated 01/18/2011 06:51 PM
Does the FAA require children on commercial flights to be in child restraint systems (CRS)?
The FAA does not require the use of CRS's on commercial airplanes because a mandate would require parents to purchase an extra airline ticket for their child, forcing some families who can't afford the extra ticket to drive, a statistically more dangerous way to travel. However, the FAA strongly recommends the use of CRS's or an alternative FAA-approved device based on a child's weight. A child safety device is an FAA-approved alternative to using a hard-backed seat and is approved only for use on aircraft. It is not approved for use in motor vehicles. For example, the FAA has approved a new harness-type device appropriate for children weighing between 22 and 44 pounds. Airlines currently allow children under the age of two to fly free of charge as "lap children," not the safest way for a child to travel. Many airlines offer half-price tickets so parents can be guaranteed that their child can travel in a CRS or device. Parents should call their airline to ask for a discount and/or ask what the airline's policy is for using empty seats.