- A retractable landing gear (land aircraft only; a seaplane is not required to have this)
- A controllable-pitch propeller (which includes airplanes with constant-speed propellers and airplanes with FADEC which controls both the engine and propeller).
- Movable or adjustable flaps.
The current FAA definitions of "Complex Airplane", either from the Airplane Flying Handbook FAA-H-8083-3B Chapter 11 or from FAA Order 8900.2C, require the airplane to have a propeller. This means that essentially no turbojet and turbofan airplanes (the only exception would be very rare mixed-propulsion airplanes) are "complex" per the FAA definition.
Before or after earning the private pilot certificate (PPL) (usually after), a pilot can be trained in complex aircraft operation by a flight instructor. When the pilot has demonstrated proficiency in complex aircraft, the flight instructor endorses the pilot's logbook and the pilot is said to have a "complex endorsement".
As of April 24, 2018 the FAA requires a commercial pilot applicant and CFI applicant to have experience in a complex aircraft; however, the practical test may be taken in a non-complex aircraft for the commercial pilot certificate (CPL) and the flight instructor certificate (CFI).
- 14 C.F.R., Sec. 61.31(e)
- 8900.2 – General Aviation Airman Designee Handbook
- N_8900.463 – Use of a Complex Airplane During a Commercial Pilot or Flight Instructor Practical Test