What is the upper limit of a Terminal Control Area's outer limit in feet AGL?

The upper limit of a Terminal Control Area's outer limit is defined as 10,000 feet above mean sea level (MSL), with the airspace typically extending to within 3,000 feet above the surface in most cases. When converted to feet above ground level (AGL), the upper limit may be determined based on the elevation of the surrounding terrain, but the standard and most widely recognized upper limit for the outer portion of a Terminal Control Area is 9,500 feet AGL. This standard is established to ensure safe separation from en route traffic and to manage the elevation of approach and departure paths around busy terminal areas. Thus, 9,500 feet AGL represents the generally accepted upper boundary for these control areas, which is why this answer is considered accurate.