A flight instructor is a person who teaches others to fly aircraft. Specific privileges granted to holders of a flight instructor qualification vary from country to country, but very generally, a flight instructor serves to enhance or evaluate the knowledge and skill level of an aviator in pursuit of a higher pilot's license, certificate or rating.
United States 
A person who holds a flight instructor certificate (called a "Certificated Flight Instructor" or CFI) is authorized to give training and endorsements required for and relating to:
- a student, private, commercial or other pilot certificate;
- the 3 hours of training with reference only to instruments in preparation for a Private Pilot certificate, note that this does not need to be a CFII.
- an Instrument Rating, only if the CFI has an Instrument Instructor Rating (CFII); This cannot be given by a "safety pilot". A safety pilot can only be used to help maintain instrument proficiency with an instrument-rated pilot by flying the required six instrument approaches-holding-intercepting/tracking courses, within preceding six calendar months.
- a Flight Instructor Certificate is only given if he has met the experience requirements (detailed below);
- a flight review, endorsement (previously called BFR) (currently referred to as FLIGHT REVIEW see 14 CFR part 61.56), or recency of experience requirement;
- preparation for a practical test (typically three hours within the preceding 60 days in preparation for a certificate or rating); or
- endorsement for a knowledge test (written examination)
Certain limitations are placed on the instruction a flight instructor may give. For example, flight instructors wishing to train applicants for a flight instructor certificate must have held their own flight instructor certificate for at least 24 months and given at least 200 hours of instruction. Specific training programs have additional requirements or limitations.
Eligibility requirements 
Flight instructors in the United States must hold at least a commercial pilot certificate or ATP (Airline Transport Pilot) certificate. Individuals wishing to give instruction in airplanes or powered-lift aircraft are additionally required to hold an instrument rating in the desired category and class. Holders of a sport pilot certificate may obtain a flight instructor certificate with sport pilot rating, allowing them to give instruction for the sport pilot certificate in light-sport aircraft.
All individuals desiring flight instructor privileges must pass two additional written exams (Fundamentals of Instruction, or FOI; and a knowledge test specific to the category of aircraft in which instructional privileges are desired, such as fixed-wing) as well as a practical test. Flight Instructors must be at least 18 years of age to be eligible. Those airmen who hold Commercial Privileges in Lighter-Than-Air aircraft (Balloons and Airships) have flight instructor privileges in those category and classes they have on their pilot certificate. Lighter-Than-Air flight instructor privileges do not get placed on a Flight Instructor Certificate.
Professional organization 
This section currently covers only the aeroplane flight instructor ratings.
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.
In order to give instruction towards the instrument rating, multi rating, type ratings, and class conversions (for example, land plane to sea plane), an instructor rating is not necessarily required. The requirements may be limited to holding a commercial or airline transport license and having met certain experience levels (such as time on type and in class). In the case of an instrument rating, the holder of a flight instructor rating can teach it even if they do not have the experience level required for non-flight instructors. Details are contained in the Canadian Aviation Regulations, Parts 401 and 421.
New Zealand 
Flight instructors in New Zealand must have a Category A, B, C, D or E flight instructor rating.
The Category E rating is specifically for conducting agricultural (top dressing, etc.) flying instruction. Category D flight instructor may conduct type ratings for any aircraft for which they hold a type rating. Category C flight instructors cannot send students on their first solo, and must operate under the supervision of a Category A or B flight instructor.
The Chief Flying Instructor (CFI) is the flying instructor responsible for all flight training at an organization.
See also 
- "FAA-H-8083-9A, AVIATION INSTRUCTOR'S HANDBOOK" (PDF). Federal Aviation Agency. 2008.
- Canadian Aviation Regulations 401.61 - Flight Instructor Ratings
- Canadian Aviation Regulations 401.69 - Privilges
- Canadian Aviation Regulations 421.62 - Flight Instructor Rating Standards
- Canadian Aviation Regulations 421.69 - Flight Instructor Rating Requirements
- Requirements to become a CFI
- Computer Testing Supplement for Flight and Ground Instructor FAA 2001
- Derek W Beck's Flight Instructor Resources - Lesson Plans, Tutorials, and Explanations of Maneuvers
- Flight Instructor Directory