The aisle chairs used by individual airlines/airports may vary a little in appearance.
In general, they are:
- narrow enough to fit down the aisle
- have a hard upholstered seat, back and headrest
- have straps for securing at the legs, waist/hips, chest and they will also strap the arms for people who are not able to keep their arms in.
The aisle chair will be parked next to the wheelchair and then either you or the airline staff will lift your child into the aisle chair. They will take care of securing the various belts, wheeling the chair into the plane and unfastening all the belts.
Then they, or you will transfer the child to the plane seat. If you want to do the lifting yourself, let them know. We have always found staff very appreciative of whatever hints we can offer in terms of things like where to place the wheelchair in relation to the aisle chairs, how to lift, etc.
There is more information (and pictures) in the disABILITIES FAQs thread, which you can find near the top of this board or follow the link in my signature. The post about air travel in the last one on page 1.
My DD is in the pictures and is about 5 feet tall and 80-85 pounds if that helps you figure things out.
Post 2 of the disABILITIES FAQs thread has information about renting equipment. It starts out with wheelchairs and
ECVs , but near the bottom there is a list of companies that rent medical equipment. Several rent various types of shower chairs.