Can multiple airfields be in the same airspace?
When there are several airports close to each other, a single ATC, formally known as Terminal Control Center may service all airports. The airspace boundaries and altitudes assigned to a Terminal Control Center, which vary widely from airport to airport, are based on factors such as traffic flows, neighboring airports and terrain.

London Terminal Control Centre is an example of a large and complex Terminal Control Center. Its service area is up to 20,000 feet and out to 100 nautical miles. It controls:


six London airports
one Royal Air Force station
provides en-route services to other aircraft that entered its airspace


Another example can be found with Berlin-Tegel and Berlin-Schönefeld, which have adjacent control zones that share a common boundary west to east and have an overlaying class C TMA airspace up to FL100. Both airports share the same TMA controller/approach sector:BREMEN RADAR Approach:    119.62

Image Source: www.skyvector.com



FAA is implementing a new airspace system which will increase efficiencies at metropolitan areas with complex air traffic flows. This system, known as Next Generation Air Transportation System is introducing the concept of a metroplex:


  In FAA parlance, metroplex refers to a system of airports in close
  proximity and their shared airspace that serve one or more major
  cities. A metroplex has at least one, but often two or more major
  commercial airports.