2010 ADA Standards for Accessible Design Pocket Guide

802.3.1 Alignment.

In row seating, companion seats shall be located to provide shoulder alignment with adjacent wheelchair spaces. The shoulder alignment point of the wheelchair space shall be measured 36 inches (915 mm) from the front of the wheelchair space. The floor surface of the companion seat shall be at the same elevation as the floor surface of the wheelchair space. [S.H. 4.33.3]