ICAO Annex 6: Operation of Aircraft

ICAO Annex 6, Operation of Aircraft, is the annex to the Chicago Convention that governs how flights are conducted. Where Annex 1 licenses the pilot and Annex 8 certifies the aircraft, Annex 6 sets the Standards and Recommended Practices (SARPs) for the operation itself: who may run an airline, how a flight is prepared, what fuel it carries, which equipment and recorders it needs, and how its crew are trained and protected from fatigue. It contains the SARPs on which an air operator certificate (AOC) for international commercial air transport is issued.

It binds no pilot directly. SARPs are not legally binding until a State embodies them in national law; a State that departs from a Standard must notify ICAO under Article 38, and it lists its significant differences in its AIP (see the Chicago Convention and ICAO). Europe applies Annex 6 through the Air Operations Regulation, (EU) No 965/2012; the United States through 14 CFR Parts 91, 119, 121, 135 and 117.

Structure: Parts I, II and III

Annex 6 is published in three parts, each with its own editions and amendments:

ICAO sorts operations into three families. Commercial air transport carries passengers, cargo or mail for remuneration or hire. Aerial work uses an aircraft for specialized services such as agriculture, surveying or aerial advertisement, which EASA regulates as specialized operations under Part-SPO. General aviation is everything else (see commercial and private operations).

Part II addresses many of its rules to the pilot-in-command rather than to an operator. The EU divides the same ground between complex aircraft, under Part-NCC, and other-than-complex aircraft, under Part-NCO, and France lists where the two differ: Part-NCC addresses to the operator a rule that Annex 6 addresses to the pilot-in-command, and the EU definition of a complex airplane, which by seating takes in only airplanes with more than 19 passenger seats, is filed as less protective than Annex 6.

Part III applies the same split to helicopters, with one section for international commercial air transport and one for international general aviation. Where the safe continuation of a flight is not ensured if the critical engine fails, it requires helicopter operations to give appropriate consideration to achieving a safe forced landing. EASA's helicopter performance classes grow out of it, sorted by what a critical engine failure would allow. In class 1 the helicopter can either land within the rejected takeoff distance or continue safely, whenever the failure occurs; in class 2 it can continue safely except early in the takeoff or late in the landing, when a forced landing may be required; in class 3 an engine failure at any time may require a forced landing, and in a single-engine helicopter will. EASA's guidance describes class 2 as based primarily on the commercial section of Part III.

Annex 6 complements Annex 8: Annex 8 treats airworthiness from the engineering side, Annex 6 from the operational side. The text changes often; in October 2025 France compared its rules with Part I in its 12th edition including Amendment 49, Part II in its 11th edition including Amendment 41, and Part III in its 11th edition including Amendment 25.

Operator responsibilities and the AOC

Part I builds everything around the operator. The State of the Operator, where the operator has its principal place of business, issues the AOC and oversees the operator. The AOC and its operations specifications name the operator, the types of operation, the aircraft types and registration marks, the areas of operation and any special limitations and authorizations; the maximum takeoff mass of each aircraft is not among them (see air operator certification).

Operational control is the exercise of authority over the initiation, continuation, diversion or termination of a flight. The operator may delegate it only to the commander and, where its approved method of supervision requires one, to a flight operations officer or dispatcher (see operational control and flight dispatch). EU rules leave it solely with the commander. In US domestic and flag operations, by contrast, the pilot in command and the aircraft dispatcher are jointly responsible for planning and releasing each flight.

The operator must also provide:

• an operations manual for its personnel, with the normal, abnormal and emergency procedures and their checklists; EASA divides it into Parts A to D under ORO.MLR (see operations manual and flight crew documentation);
• a maintenance program;
• a flight data analysis program as part of its safety management. ORO.AOC.130 requires one for airplanes over 27,000 kg maximum certificated takeoff mass and requires it to be non-punitive; France lists as differences that Annex 6 also reaches lighter airplanes, some down to 15,000 kg, which the EU rule does not cover.

Flight preparation and operating minima

Each flight is prepared on an operational flight plan, the operator's plan for its safe conduct based on the airplane's performance and limitations and the conditions expected. The EU does not require one for VFR flights by other-than-complex airplanes that take off and land at the same aerodrome, a gap France lists.

The operator establishes aerodrome operating minima, the limits of usability of an aerodrome, for every aerodrome it plans to use. They may not be lower than those set by the State in which the aerodrome lies, unless that State specifically approves (CAT.OP.MPA.110). EASA, following ICAO, classes approaches by their minima: Type A has an MDH or DH at or above 250 ft; Type B has a DH below 250 ft and three categories (see aerodrome operating minima):

Where the DH and the RVR fall into different categories, current ICAO guidance applies the more demanding one. Older EU-OPS texts let the RVR alone decide and split CAT III into IIIA, IIIB and IIIC, a subdivision the FAA still uses.

Fuel and alternates

Annex 6 recognizes three kinds of alternate (see alternate aerodromes):

• A takeoff alternate, for when the airplane could not return to the departure aerodrome shortly after takeoff: within 1 hour at one-engine-inoperative cruise speed for a twin, and within 2 hours at all-engines-operating cruise speed with three or four engines. EU-OPS and 14 CFR 121.617 measure the 2 hours at one-engine-inoperative speed.
• A destination alternate, to which the flight may proceed when landing at the destination becomes impossible or inadvisable.
• An en-route alternate for a problem in the cruise. For long-range twins Annex 6 speaks of extended diversion time operations (EDTO); the EU rules still use ETOPS.

The EU requires the forecast at a takeoff or destination alternate to meet the minima from 1 hour before to 1 hour after the estimated time of arrival there; for the takeoff alternate France files this as more exacting than Annex 6.

The usable fuel is a stack of blocks: taxi, trip, contingency, destination alternate, final reserve, additional fuel for the most critical failure where the others would not cover it, and discretionary fuel at the commander's discretion; EASA adds extra fuel for anticipated delays or specific operational constraints. Under EASA's basic fuel scheme (AMC1 CAT.OP.MPA.181), contingency is the higher of 5 percent of trip fuel and 5 minutes' holding at 1,500 ft above the destination, and the final reserve is 30 minutes' holding at 1,500 ft (450 m) above aerodrome elevation for turbine airplanes, 45 minutes for piston airplanes. An EU operator wanting an individual fuel scheme must first collect two years of data (see fuel planning and fuel reserves).

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In flight, MINIMUM FUEL tells ATC that the airplane is committed to land at a specific aerodrome and any change to the clearance may lead to landing below the planned final reserve; it is not an emergency. MAYDAY MAYDAY MAYDAY FUEL is required when the calculated usable fuel on landing at the nearest aerodrome where a safe landing can be made is below the final reserve (see in-flight fuel management). The FAA states reserves as fixed times instead, such as 45 minutes at normal cruising consumption after the most distant alternate for US domestic operations (121.639).

Equipment and recorders

The equipment chapters set what an airplane must carry, with thresholds by mass, seating and date of first certificate of airworthiness. Figures often examined:

The flight data recorder keeps at least 25 hours on most commercial airplanes, and the underwater locator beacon on each recorder transmits at 37.5 kHz for at least 90 days, 30 days on older units (see flight recorders). The EU requires a further 8.8 kHz underwater locating device on airplanes over 27,000 kg with more than 19 passenger seats and on all airplanes over 45,500 kg, a narrower scope than Annex 6 that France files as partially implemented. Annex 6 also asks for a means of locating an airplane in distress while still in flight; France lists an ELT triggered in flight or an automatically deployable flight recorder (see emergency beacons).

Annex 6 also requires the flight crew compartment door to stay closed and locked from the closing of all external doors after embarkation until one opens for disembarkation, except to let authorized persons through; the FAA's 14 CFR 121.587 is worded differently.

Flight crew and fatigue

The operator runs a ground and flight training program approved by the State of the Operator, covering human performance including threat and error management. ICAO amended Annex 1 and Annex 6 with effect from 13 November 2014 to add upset prevention and recovery training. In the EU, ORO.FC adds initial and recurrent CRM training and an operator proficiency check valid for 6 calendar months plus the remainder of the month of issue, or an approved alternative training and qualification program or evidence-based training instead.

Annex 6 also sets standards for recent experience, route and aerodrome qualification of the commander, and proficiency checks. Part-FCL implements recency in FCL.060: 3 takeoffs, approaches and landings in the preceding 90 days, in the same type or class or a full flight simulator. EASA adds 5 IFR flights including 3 instrument approaches for single-pilot IFR (ORO.FC.202), and sorts aerodromes into categories A, B and C for route and aerodrome qualification.

Flight time, in the ICAO definition, runs from the moment an airplane first moves for the purpose of taking off until it finally comes to rest at the end of the flight, so a pushback counts. The FAA's definition in 14 CFR 1.1 starts when the aircraft moves under its own power for the purpose of flight.

ICAO treats fatigue as a physiological state of reduced mental or physical performance caused by sleep loss, extended wakefulness, circadian phase or workload. Annex 6 requires the State of the Operator to regulate it on scientific principles and operational experience, with prescriptive limits on flight time, flight duty periods, duty periods and rest, and lets it approve an operator's fatigue risk management system (FRMS) for all or part of its operations; ICAO Doc 9966 describes how. Europe's prescriptive scheme is ORO.FTL with CS FTL.1; the FAA's is 14 CFR Part 117, applied to Part 121 passenger operations since 4 January 2014 (see flight time limitations).

How EU Air OPS and FAA rules implement Annex 6

The EU writes the essential requirements into its Basic Regulation, (EU) 2018/1139, and the detail into the Air OPS Regulation, (EU) No 965/2012 (see EASA regulatory framework). Part-ORO carries the operator requirements of Part I: the AOC, the management system, crew training and checking, flight time limitations and the operations manual. Part-CAT governs commercial flights, with the fuel/energy scheme and all-weather rules applicable since 30 October 2022; Part-SPA grants specific approvals such as low visibility operations, RVSM and ETOPS; Part-NCC and Part-NCO cover Part II.

France's AIP GEN 1.7 grades each difference as more exacting, different in character or other means of compliance, or less protective, which includes partly or not implemented. Among its Annex 6 entries:

• more exacting: flight data monitoring must be non-punitive whatever the airplane's date, and single-pilot IFR has its own recency;
• different in character: the AOC has no expiry date, and operational control rests solely with the commander;
• partly or not implemented: EDTO, for which the EU keeps ETOPS, and the duties of flight operations officers and dispatchers.

In the United States, Part 119 issues the air carrier or operating certificate with operations specifications, the US form of the AOC; Parts 121 and 135 hold the operating rules corresponding to Part I; Part 91 covers general aviation; Part 117 regulates fatigue; and Part 5 requires a safety management system for Part 121 carriers (see FAA Part 121 air carrier operations). The differences most often examined are the definition of flight time, CAT III still split into IIIa, IIIb and IIIc, fuel reserves stated as fixed times, and the dispatcher sharing operational control.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.