In Canada, the holder of a commercial pilot licence or airline transport pilot licence may have their licence endorsed with a flight instructor rating - aeroplane. Initially, the pilot is endorsed as a Class 4 flight instructor. This allows the pilot to deliver flight training towards the issuance of a Recreational Pilot Permit, Private Pilot Licence, Commercial Pilot Licence, Night Rating, and VFR Over-the-top Rating. The Class 4 flight instructor may only conduct training while under the supervision of a Class 2 or Class 1 flight instructor.
After satisfying certain requirements (satisfactory flight test records, experience requirements, written exams, and flight tests), an instructor can upgrade their rating to a Class 3, Class 2, and Class 1 instructor rating. The Class 3 flight instructor does not require the supervision of a Class 2 or Class 1 flight instructor. The Class 2 flight instructor may supervise Class 4 flight instructors and act as the Chief Flight Instructor (CFI) of a flight training unit. The Class 1 flight instructor may give ground school and flight training towards the endorsement of a flight instructor rating.
As much as I hate to rely on the information being correct on Wikipedia,
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