If you're flying through a Canadian airport and staying in a sterile transit area, or going through US preclearance facilities, you are not considered to be seeking entry into Canada, you're applying to transit. However, if an officer flags you, they can still conduct a full examination even if you're just transiting.
(1)Subject to subsection (2), the following persons are not seeking to enter Canada but are making an application under subsection 15(1) of the Act to transit through Canada: (a)in airports where there are United States’ in-transit preclearance facilities, in-transit preclearance passengers; and (b)in any airport, passengers who are arriving from any country and who are transiting to a country other than Canada and remain in a sterile transit area.
(2)Any person seeking to leave a sterile transit area must appear immediately for examination.