Unraveling Applicability: The FAA Operational Requirements 14 CFR Parts 135, 121, and 125

As you may know, FAA Title 14 CFR Parts 135, 121, and 125 define the Operational Requirements for various types of operations conducted in U.S. airspace.  But do you know when each one applies? This can get a bit tricky, so I’ll try to unravel the applicability of the operational requirements for various passenger carrying operations.

Specific attributes of the operation, design, and configuration of the aircraft are used to determine which of these three Operational Requirements are applicable to a particular operation to be certified.

FAA Operational Requirements

The three FAA Title 14 operational requirements and their full titles are:

  • Part 135 – Operating Requirements: Commuter And On Demand Operations And Rules Governing Persons On Board Such Aircraft
  • Part 121 – Operating Requirements: Domestic, Flag, And Supplemental Operations
  • Part 125 – Certification And Operations: Airplanes Having A Seating Capacity Of 20 Or More Passengers Or A Maximum Payload Capacity Of 6,000 Pounds Or More; And Rules Governing Persons On Board Such Aircraft

Size of the aircraft

The distinction between 14 CFR Part 135 and 14 CFR Parts 121 and 125 is primarily the size of the aircraft as defined by the maximum payload weight and seating capacity for passengers in which the operations are conducted. In general, 14 CFR Part 135 are for commercial passenger and cargo operations conducted in smaller aircraft and Parts 121 and 125 are for such operations conducted in larger aircraft.

Common carriage

The distinction between 14 CFR Parts 121 and 125 is made by determining whether or not the operations involve common carriage.  Common carriage is when a carrier “’holds itself out’ to the public or to a segment of the public, as willing to furnish transportation within the limits of its facilities to any person who wants it. … There are four elements in defining a common carrier; (1) a holding out of a willingness to (2) transport persons or property (3) from place to place (4) for compensation. This ‘holding out’ which makes a person a common carrier can be done in many ways and it does not matter how it is done” (FAA AC 120-12A).  A common way an operator holds itself out is by advertising its services.  However, holding out may be performed without advertising if the operator has a sufficient reputation of providing their services to all who desire and pay the requested compensation.  Holding out is essentially an expression of willingness to all customers with whom contact is made that the operator will perform the requested services.

Pulling it all together

Below are two tables I created that present the attributes necessary to distinguish the applicable Operational Requirements for a particular operation. The Table 1 is for common carriage operations and Table 2 is for operations where common carriage is not involved. The information contained in these tables was derived from regulations 14 CFR Sec. 110.2 Definitions, 14 CFR Sec. 119.21, and 14 CFR Sec. 119.23.

[Click on each image below to view a full size version of the table.]

Stump the blogger

Got a tricky operation that you are stumped on (or think you can stump me on)?  Post a description of it and I’ll take a shot at identifying the FAA Operational Requirements that are applicable.


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