From what I've understood, in Canada a Terminal Control Area (TCA) is established at airports with a high volume of traffic to provide IFR control service to arriving, departing and en route aircraft.

A Control Zone is designed around aerodromes to keep IFR aircraft within controlled airspace.

Why do we have both? Both provide ATC services, so why do we require a Control Zone within a TCA? Is there a specific reason that the TCA cannot be lowered below 700 AGL?

See this reference material in "From The Ground Up" (I've tried to attach it but it didn't work).

  • 1
    $\begingroup$ If you're using From The Ground Up, you're asking about Canadian Regs? They are largely similar, but there are subtle differences between Can and FAA Regs so it's important to make the distinction. $\endgroup$
    – John K
    Mar 6, 2019 at 21:33
  • 2
    $\begingroup$ @JohnK The OP used the "canada" tag, so I'd say that they are talking about Canadian regulations. $\endgroup$
    – Ron Beyer
    Mar 6, 2019 at 21:36

1 Answer 1


A Control Zone is the small (and usually circular) surface area around the airport that is handled by the airport's control tower. At smaller airports (but still large enough to have a tower), this is all they have.

A Terminal Control Area is a large and typically complex area above one or more Control Zones to manage large flows of fast traffic (i.e. airliners) moving in both directions through the congested area between the Control Zone(s) and the en route environment far above.

Note that while Canada (and the US, though it uses very different terminology) often uses the same class of airspace for the TCA and CZ, that isn't required, and there may even be several CZs with different classes under one TCA.

  • $\begingroup$ Important point: a control zone always touches the ground, a terminal area does not. $\endgroup$ Mar 7, 2019 at 20:53

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