 Specially designed transfer chairs are now required features at airports in much of the developed world in order to allow access down narrow airliner aisles and facilitate the transfer of wheelchair-using passengers to and from their seats on the aircraft.An electric-powered wheelchair, commonly called a "powerchair" is a wheelchair which additionally incorporates batteries and electric motors into the frame and that is controlled by either the user or an attendant, most commonly via a small joystick mounted on the armrest, or on the upper rear of the frame.Alternatives exist for the traditional manual joystick, including headswitches, chin-operated joysticks, sip-and-puff controllers or other specialist controls, which may allow independent operation of the wheelchair for a wider population of users with varying motor impairments.