FAA Part 121: Air Carrier Operations
14 CFR Part 121 is the FAA rule book for air carriers and commercial operators certificated under Part 119 to conduct domestic, flag and supplemental operations: in practice the scheduled airlines and the larger charter and cargo carriers. It adds dispatch, crew, fuel and equipment requirements to the general rules of Part 91.
14 CFR Part 121 is the set of FAA operating rules under which US airlines fly. It applies to operators certificated under Part 119 for domestic, flag and supplemental operations, which in practice means the scheduled passenger airlines, from the regional carriers to the majors, and the larger charter and all-cargo operators. Part 121 does not replace the general operating rules of Part 91; it adds to them, so an airline crew obeys both.
What Part 121 adds is structure around each flight. An FAA-certificated aircraft dispatcher shares operational control with the captain, every flight leaves under a signed release, fuel and alternates follow fixed formulas, and the pilots must meet experience, training and recency standards well above those of the certificates alone. The European counterpart is Part-CAT, with the operator certificated under Part-ORO (see from EU-OPS to Part-CAT). Smaller commuter and on-demand operators fly under Part 135 (see FAA Part 135 and Part 119).
- Part 119 certificates and Part 121
- Domestic, flag and supplemental operations
- Operational control, dispatch and the flight release
- Fuel and alternate requirements
- Crew qualification, experience and recency
- Flight attendants, cabin rules and the sterile flight deck
- Part 117, Part 120 and other linked rules
- Frequently asked questions
Part 119 certificates and Part 121
Part 119 decides which certificate an operator needs and which operating part then applies (see air operator certification). An operator that provides air transportation as a direct air carrier receives an air carrier certificate; one that carries persons or property for compensation or hire without being an air carrier receives an operating certificate. The FAA then issues operations specifications (OpSpecs), numbered paragraphs that authorise particular approaches, minima, routes and equipment.
A Part 121 certificate holder must employ a Director of Safety, a Director of Operations, a Chief Pilot, a Director of Maintenance and a Chief Inspector, and under Part 5 it must run a safety management system under an accountable executive. The dividing line with Part 135 depends on whether the flights are scheduled, the number of passenger seats, the payload capacity and whether the aircraft is a turbojet: a scheduled passenger service in a turbojet is a Part 121 operation however few seats the aeroplane has.
Domestic, flag and supplemental operations
The three kinds of Part 121 operation are defined in 14 CFR 110.2. They matter because different sections of Part 121 apply to each.
| Kind | Scope in outline | Release | Shares operational control with the pilot in command | Fuel rule |
|---|---|---|---|---|
| Domestic operation | Scheduled, within the 48 contiguous states, or within Alaska or Hawaii | Dispatch release | Aircraft dispatcher | 121.639 |
| Flag operation | Scheduled, between the US and points outside it, between points outside it, or between the 48 states and Alaska or Hawaii | Dispatch release | Aircraft dispatcher | 121.645 for turbojets outside the 48 states |
| Supplemental operation | Non-scheduled with larger aeroplanes, and larger all-cargo operations | Flight release | Director of operations | 121.645 for turbojets outside the 48 states |
Alternate rules also differ: 121.619 for domestic flights, 121.621 for flag flights.
Operational control, dispatch and the flight release
Operational control, in 14 CFR 1.1, is the exercise of authority over initiating, conducting or terminating a flight. The certificate holder is responsible for it and exercises it through named people (see operational control and flight dispatch).
In domestic and flag operations the pilot in command and the aircraft dispatcher are jointly responsible for the pre-flight planning, delay and dispatch release of each flight (121.533 and 121.535), and both sign the release (121.663). Under 121.687 the dispatch release contains:
- the aircraft identification number and trip number;
- the departure, intermediate, destination and alternate airports;
- the type of operation, IFR or VFR;
- the minimum fuel supply;
- the latest available weather reports and forecasts, or a statement that they are attached.
The dispatcher must know the weather on the route, gives the captain the reports and forecasts that may affect the flight and passes on information needed for safety while it is airborne (121.599 and 121.601), monitors its progress, and cancels or redispatches a flight that cannot continue safely as released (121.533 and 121.535). In supplemental operations the document is a flight release, and the director of operations shares operational control with the pilot in command (121.537); a flight-following system keeps track of each flight.
Joint planning stops at take-off. During flight time the pilot in command has full control and authority over the aircraft and crew. In an emergency calling for immediate action, 121.557 lets the captain deviate from procedures, weather minima and the regulations as far as safety requires, keeping ATC and dispatch informed and sending the FAA a written report, through the operations manager, within 10 days of returning to home base.
Weather at dispatch
A flight may be released under IFR only if the reports and forecasts show the destination at or above the authorised minima at the estimated time of arrival (121.613). A domestic flight needs a destination alternate unless, for at least 1 hour before to 1 hour after the ETA, the forecast ceiling is at least 2,000 ft above the airport elevation and the visibility at least 3 statute miles (121.619). A flag flight may dispense with an alternate if it is scheduled for 6 hours or less and the forecast meets a stricter test (121.621). An alternate must be forecast at or above the alternate minima in the OpSpecs (121.625): under the standard paragraph C055, 400 ft and 1 statute mile are added to the minima of an airport with one navigation facility, or 200 ft and ½ mile to the higher of two approaches to different suitable runways.
If the departure weather is below the landing minima, 121.617 requires a take-off alternate within 1 hour for a twin, or 2 hours for an aeroplane with three or more engines, at one-engine-inoperative cruise speed in still air.
Exam tip: the 600-2 and 800-2 standard alternate minima belong to Part 91 (91.169) and do not govern a Part 121 release. Part 121 also has an approach ban that Part 91 lacks: under 121.651 a crew may not begin the final approach segment when the reported visibility is below minimums, although a report that drops after the final approach fix does not force a go-around.
Fuel and alternate requirements
Part 121 states minimum fuel as a fixed sequence.
| Rule | Applies to | Fuel required |
|---|---|---|
| 121.639 | Domestic operations | To the destination, then to the most distant alternate when one is required, then 45 minutes at normal cruising fuel consumption |
| 121.645 | Turbojets on flag and supplemental operations outside the 48 contiguous states | To the destination, then 10 per cent of the total flight time from departure to destination, then to the most distant alternate if required, then 30 minutes holding at 1,500 ft above the alternate (or the destination if no alternate is required) in standard temperature |
Whatever the rule, 121.647 requires the calculation to take account of the forecast wind and weather, anticipated traffic delays, one instrument approach and a possible missed approach at the destination, and any other condition that may delay the landing. Dispatchers add contingency fuel above the legal minimum, and the captain may add fuel but may not accept less than the release specifies. Redispatch planning can reduce the 10 per cent component, and twins planned more than 60 minutes from an adequate airport, at one-engine-inoperative cruise speed, also need ETOPS approval and critical fuel (see ETOPS). The EASA approach is compared in fuel planning and fuel reserves.
Crew qualification, experience and recency
Since 2013, 121.436 has required every Part 121 pilot to hold an airline transport pilot (ATP) certificate with the type rating. A first officer may hold a restricted ATP, available from 750 hours for military pilots, 1,000 hours for graduates of an approved bachelor's degree programme with 60 credit hours of aviation coursework, or 1,250 hours with an associate degree, instead of the normal 1,500 hours (see restricted ATP). A captain needs at least 1,000 hours of air carrier experience, normally as second in command in Part 121 operations, although pilot in command time in Part 91 subpart K, Part 135 or military operations can count within limits. The ATP certification training programme of 61.156 came with the rules that followed the Colgan Air Flight 3407 accident.
After the airline's training programme, each pilot completes operating experience under a check airman, at least 25 hours in a two-pilot turbojet in either seat (121.434), and a new captain also passes a line check. To consolidate the training, the pilot must fly at least 100 hours of line operations within 120 days of completing it (121.434(g)). Other rules build on that:
- Recency (121.439): three take-offs and three landings in the type within the preceding 90 days, which may be made in a simulator approved for the purpose.
- High minimums (121.652): until a captain has 100 hours as pilot in command in the type in Part 121 operations, 100 ft is added to the DA or MDA and ½ mile, or the RVR equivalent, to the visibility, never below 300 ft and 1 mile.
- Special airports (121.445): airports that the FAA designates because of their terrain or unusual procedures, listed in OpSpec C050, call for a special airport qualification of the captain, for which airlines provide pictorial familiarisation, so that the crew knows the terrain and procedures before operating there in poor weather.
- Age (121.383): no pilot may serve as a required pilot in Part 121 operations after reaching 65.
Flight attendants, cabin rules and the sterile flight deck
The number of flight attendants depends on the aeroplane's passenger seating capacity, not on the number of passengers carried (121.391).
| Passenger seats | Flight attendants |
|---|---|
| 10 to 50, maximum payload above 7,500 lb (20 to 50 if 7,500 lb or less) | 1 |
| 51 to 100 | 2 |
| More than 100 | 2, plus 1 for each unit or part of a unit of 50 seats above 100 |
Passengers receive an oral briefing before each take-off on smoking, exits, seat belts and any flotation equipment (121.571). Exit-row passengers must meet the selection criteria of 121.585, which include being at least 15 years old, and the seat belt sign is on during any movement on the surface, for every take-off and landing, and whenever the captain considers it necessary (121.317). The reinforced flight deck door stays closed and locked whenever the aircraft is being operated, except when necessary to let persons authorised under 121.547 in or out (121.587).
The sterile flight deck rule, 121.542, bars every duty not required for the safe operation of the aircraft during critical phases of flight: all ground operations involving taxi, take-off and landing, and all other flight below 10,000 ft except cruise. The captain may not permit any activity that could distract a crewmember, and a 2014 amendment bans personal use of wireless devices and laptops at the duty station during flight time. In the Colgan Air accident the crew continued a conversation unrelated to the flight below 10,000 ft, and the NTSB found their failure to adhere to sterile cockpit procedures a contributing factor. EASA's equivalent, CAT.GEN.MPA.105, protects defined critical phases instead (see attention, vigilance and distraction).
Part 117, Part 120 and other linked rules
Several other parts complete the Part 121 picture:
- Part 117 sets the flight and duty limits for flightcrew members in passenger operations: at least 10 consecutive hours of rest, including an opportunity for 8 hours of uninterrupted sleep, before a flight duty period, an affirmation of fitness for duty before each flight, and cumulative limits such as 100 flight hours in any 672 consecutive hours (see flight time limitations).
- Part 120, which replaced Appendices I and J of Part 121, requires drug and alcohol testing of safety-sensitive staff, pilots included: pre-employment, random, reasonable-suspicion, post-accident, return-to-duty and follow-up tests. A refusal counts as a positive result.
- Part 5 requires the safety management system, and Part 111 the Pilot Records Database, which a hiring carrier must review with the pilot's consent.
- Part 91 still applies underneath: the standard take-off minima that 91.175(f) sets for Part 121 and 135 operators, where Part 97 prescribes none for the airport, are 1 statute mile for aeroplanes with two engines or fewer and ½ mile with more than two, with lower values available through OpSpec C078.
For the career route into a Part 121 cockpit, see how to become an airline pilot in the USA.
Frequently asked questions
What is the difference between Part 91, Part 121 and Part 135?
Part 91 holds the general operating and flight rules that apply to almost every civil aircraft in the United States. Part 121 and Part 135 are operating rules for certificate holders under Part 119 and add to Part 91 rather than replace it. Part 121 covers the domestic, flag and supplemental operations of the airlines and larger carriers; Part 135 covers commuter and on-demand operations with smaller aircraft.
What are domestic, flag and supplemental operations?
They are the three kinds of Part 121 operation, defined in 14 CFR 110.2. Domestic operations are scheduled flights within the 48 contiguous states, or within Alaska or Hawaii. Flag operations are scheduled flights between the United States and points outside it, between points outside it, or between the 48 states and Alaska or Hawaii. Supplemental operations are non-scheduled flights with larger aeroplanes and larger all-cargo operations.
How much fuel must a Part 121 airliner carry?
A domestic flight needs fuel to the destination, then to the most distant alternate when one is required, then 45 minutes at normal cruising fuel consumption (121.639). Turbojets on flag and supplemental operations outside the 48 contiguous states use 121.645 instead, adding 10 per cent of the flight time to the destination and 30 minutes of holding at 1,500 ft above the alternate. Winds, expected delays and an approach and missed approach must be allowed for.
What does the sterile flight deck rule prohibit?
Under 14 CFR 121.542 no crewmember may perform any duty during a critical phase of flight except those required for the safe operation of the aircraft, and the pilot in command may not allow activities that could distract the crew. Critical phases are all ground operations involving taxi, take-off and landing, and all other flight below 10,000 ft except cruise. Since 2014 personal use of wireless devices and laptops at the duty station is also banned.
What experience does a Part 121 captain need?
Under 14 CFR 121.436 a pilot in command needs an airline transport pilot certificate with the type rating and at least 1,000 hours of air carrier experience, normally as second in command in Part 121 operations, although pilot in command time in Part 91 subpart K, Part 135 or military operations can count within limits. A new captain then flies with raised landing minimums until reaching 100 hours as pilot in command in the type.
Test yourself on FAA Part 121: Air Carrier Operations
The v1prep banks cover this topic in Air Law (010), with a worked explanation for every answer. EASA ATPL, PPL, IR and CPL, the FAA written tests and type ratings for the A320, 737, A220, 787, ATR 72 and E-Jet.
Start practising →Sources and further reading
- 14 CFR Part 121, Operating Requirements, Domestic, Flag, and Supplemental Operations
- 14 CFR Part 119, Certification of Air Carriers and Commercial Operators
- 14 CFR 110.2, Definitions (kinds of operation)
- 14 CFR Part 121, Subpart U, Dispatching and Flight Release Rules
- 14 CFR 121.542, Flight crewmember duties (sterile flight deck)
- 14 CFR Part 117, Flight and Duty Limitations and Rest Requirements, Flightcrew Members
- 14 CFR Part 120, Drug and Alcohol Testing Program
- NTSB AAR-10/01, Loss of Control on Approach, Colgan Air Flight 3407
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.