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.