21 Aerospace Control and Warning Squadron was activated at St. Margarets, New Brunswick in 1953.

With its complement of 185 personnel, 21 Aerospace Control and Warning Squadron maintains air sovereignty over Canadian airspace, monitors Canada's surveillance assets and controls assigned Aircraft.

It coordinates with outside agencies to:

Identify Air Traffic (over 200,000 flights a year)

Provide control of special air sovereignty incidents

Assist law enforcement agencies with suspected Aircraft smuggling illegal drugs into North America

Support international defence and peacekeeping commitments (Bosnia, Kosovo and Iraq)

Personnel of 21 Squadron staff the "nerve center" of the Canadian Sector Air Operations Centre (SAOC) from 22 Wing's 3-story underground complex.

Five main duty crews which include aerospace controllers and aerospace control operators run the operation on eight-hour shifts. Their job is to monitor all radar feeds of air traffic approaching Canadian airspace.

Within 2 minutes, they must identify the track through a number of means, including electronic interrogation, flight plan correlation, track behavior, visual recognition or information from other agencies.

Any tracks that cannot be identified or cause suspicion are passed on to the weapons section to determine the appropriate level of response.