Canadian Domestic Airspace is geographically divided into the Southern Domestic Airspace and the Northern Domestic Airspace. In the Southern Domestic Airspace, magnetic track is used to determine cruising altitude for direction of flight. In Northern Domestic Airspace magnetic compass indications are erratic so runway heading is given in true and true track is used to determine cruising altitude for direction of flight.
Airspace is further divided vertically into low level airspace, which consists of all of the airspace below 18 000 ft ASL, and high level airspace which consists of all airspace from 18 000 ft ASL and above.
Controlled airspace is the airspace within which air traffic control service is provided and within which some or all aircraft may be subject to air traffic control. Everywhere else is known as uncontrolled airspace. Gliders in Canada are required to operate according to a set visual flight rules (VFR) and certain meteorological based criteria apply.
The altimeter setting region is an airspace of defined dimensions below 18 000 feet ASL within which prior to takeoff, the pilot sets the aircraft altimeter to the current altimeter setting of that aerodrome or, if that altimeter setting is not available, to the elevation of the aerodrome. During flights the altimeter is set to the current altimeter setting of the nearest station along the route of flight or, where such stations are separated by more than 150 NM, the nearest station to the route of flight. When approaching the aerodrome of intended landing the altimeter is set to the current aerodrome altimeter setting, if available.
The standard pressure region includes all airspace over Canada at or above 18 000 feet ASL (the high level airspace), and all low level airspace that is outside of the lateral limit of the altimeter setting region. Within the standard pressure region the altimeter is set to standard pressure, which is 29.92 inches of mercury or 1013.2 mbs. However prior to takeoff the pilot sets the aircraft altimeter to the current altimeter setting of that aerodrome or, if the altimeter setting is not available, to the elevation of that aerodrome. Immediately prior to reaching the flight level at which flight is to be conducted, the altimeter is set to standard pressure (29.92 inches of mercury or 1013.2 mbs). Before starting to descend with the intention to land, the altimeter is set to the current altimeter setting of the aerodrome of intended landing, if available. Aircraft progressing from one region to another shall make the change in the altimeter setting while within the standard pressure region prior to entering, or after leaving, the altimeter setting region. When an aircraft is operating in the standard pressure region with standard pressure set on the altimeter subscale, the term “flight level” is used in lieu of “altitude” to express its height. Flight level is always expressed in hundreds of feet. For example FL250 represents an altimeter indication of 25 000 feet; FL50, an indication of 5 000 feet.
Altitude Reservation is airspace of defined dimensions within controlled airspace that is reserved for use by a civilian or military agency during a specified period. The reservation may be for a fixed area, or follow the flight path of specific aircraft. Normally this information is published by NOTAM. These reserved areas should be avoided by all aircraft
Canadian Domestic Airspace is further divided into seven classes, each identified by a single letter – A, B, C, D, E, F, or G.