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10 Differences between FAR Part 125 versus Part 121 Regulations

Updated: Jul 29, 2022

Background on Large Group Charter Regulations

Different sets of regulations are in place for air carriers depending on the type of business they plan to conduct. As a government organization, the FAA’s responsibility is to ensure the safety of the public. As such, the FAA places a greater emphasis on protecting the general public versus private corporations.

As air travel became more popular for corporate travel over the years, many organizations created private flight departments and purchased their own aircraft. This required a new set of regulations from the FAA and the creation of Part 125. These regulations are less strict than Part 121, the regulations that all scheduled service airlines operate under. Part 125 regulations are intended for companies conducting large group business travel for 20+ passengers, not for general public travel (including charter flights). As the years went on, the line began to blur as companies started allowing other entities to “borrow” their aircraft or outright sell large group charter flights on the aircraft as a way to offset expenses or profit from their aircraft.

This has led to some big issues. Not only because federal regulations prohibit 125 operators from marketing or “holding out” services to engage in the common carriage of persons, as well as engaging in common carriage in its own right, but the end user (the passenger) is likely unaware that the operator is operating under a different set of safety regulations. For collegiate sports travel, the NCAA has even released its own statement regarding the charter of a Part 125 certified carrier for large group charter and sports team travel. In a nutshell, they do not recommend it for many of the reasons outlined below.


10. Limitations on validity of aircraft structures and components

All aircraft are amazing machines, but they are all subject to mechanical issues and eventual fatigue and breakdown of metal and parts. This is why Part 121 includes airframe "Limits of Validity". This means that all of the structural components have engineering time limits and need to be replaced over time at specific intervals. Part 125 does not include this, which means that aircraft components may be well passed their usable life and still in service.

9. Existence of Safety Management Systems

Safety is the top priority. Part 121 requires carriers to create and to implement a Safety Management System (SMS).

According to the FAA:

“An SMS is an organization-wide comprehensive and preventive approach to managing safety. An SMS includes a safety policy, formal methods for identifying hazards and mitigating risk, and the promotion of a positive safety culture. An SMS also provides assurance of the overall safety performance of [the] organization. An SMS is to be designed and developed by [the organization] and should be integrated into [the company's] existing operations and business decision-making processes. The SMS will assist [the] organization’s leadership, management teams, and employees in making effective and informed safety decisions.”

While many Part 125 operations may incorporate certain elements of a safety system, it is not mandatory, nor is it enforced.

8. Completion of Aircraft Proving Tests

How do you know if an aircraft or airline can actually operate under specific scenarios and operations? The proof is in the pudding, or more appropriately, the proof is in the proving runs. Proving runs are essentially test flights to show to the FAA that the carrier can meet certain flight criteria similar to the proposed schedule it plans to operate. Part 121 carriers are required to complete 50-100 flight hours of in depth evaluation for each kind of operation it intends to conduct, including a representative number of flights into en route airports - no passengers may be aboard the aircraft during these flights. This must be completed before they earn their 121 operating certificate. What about Part 125? No such thing is required.

Pilot Training

7. FAA approved Air Carrier specific training program required

The FAA reviews and approves certain coursework and training which is required to be completed by Pilots, Copilots, Flight Engineers, and other crew members of US Air Carriers operating under Part 121 regulations.

6. Captain and copilot both must have aircraft Type Rating

This means that for Part 121 Operators, the Captain and copilot of the aircraft both need to have received training and have been signed off by an instructor for that particular type of aircraft. Part 125 operators can have copilots who are not type rated for that particular aircraft flying a trip. This can lead to mishaps and miscommunications on the flight deck between the two pilots.

Check Airman Observation by an FAA Flight Instructor is required on a yearly basis for Part 121 and only once during initial sign off for Part 125. This means that a qualified instructor is checking the skills, safety and performance of the pilots regularly for Part 121 and not for Part 125. Part 121 operators also require their pilots to undergo Windshear Flight Instruction. This is for pilots to become familiar and comfortable taking off/landing in different extreme wind conditions, and to prove that they are capable of doing so safely in a consistent manner. Part 125 does not require this training.

5. DOT/FAA Drug Program Required

The FAA along with the Department of Transportation requires all Part 121 Air Carriers to have a Drug Program. While most Part 125 carriers do as well, it is not mandatory.

4. Maximum flight hours within 16 hours of duty

Part 121 Carriers typically do much more flying than Part 125 Carriers, and as such, the FAA limits the amount of flying a pilot can safely perform without needing a rest. The FAA has instituted specific rest requirements based on flight time. Part 125 Carriers do not have the same restrictions. So essentially they could fly for much longer without a rest, which could lead to drowsy pilots. Drowsy pilots = Dangerous.

FAA Oversight

3. 14 CFR Part 117, 119, 121 Flight crew member duty and rest requirements for passenger operations

Similar to number 4, Flight Crew are required to rest after flying a certain number of hours to prevent fatigue. The rest period is a requirement and cannot be avoided or ignored. There is also a minimum number of hours of rest required so that crews are fresh and alert between flights.

2. Federal Air Regulations operating rules Part 91 versus 121

The operating rules for Part 125 air carriers falls under part 91 (private aviation) versus Part 121 (regional/ major airlines). This major difference means that carriers operating under Part 125 have greater flexibility in their overall operating rules and less governance by the FAA since they operate more like privately owned and operated aircraft. The protections put in place by the FAA for the general flying public, does not apply in these cases to part 91, as it is designed for private usage and not for public flying.

1. FAA Surveillance High versus Low.

The Federal Aviation Administration is responsible for keeping a very close eye on all air carriers who hold a Part 121 Air Carrier Certificate and operate under Title 14 of the Code of Federal Regulations Part 121. That is their job, and as a result the United States has had very few major aircraft accidents and incidents on commercial flights. Part 121 is the pinnacle of aviation safety. It is a lengthy process to become a Part 121 operator, and rightly so.

Regulations created by the FAA (many times as a result of major accidents) are to protect the general public and to ensure compliance with the highest safety standards for air carriers across the country. If you are looking to charter a flight for a large group, do your due diligence. Air Planning will only charter flights for large groups on carriers with a Part 121 certificate. If you are considering a Part 125 certified operator, consult with your risk management and legal teams. While you could potentially save a little money on the charter flight cost, be aware of the risks.

The differences between FAR Part 121 vs FAR Part 125



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