What is Operational Control in Part 121?

Operational control defined in §1.1:

With respect to a flight, the exercise of authority to initiate, conduct, and terminate a flight.

The definition of operation control is important because it is the chain of responsibility on every step of flight in regard to your operation. 

§121.533 and §121.535 is the regulation that defines the roles and responsibility of a Part 121 domestic and flag operation. The regulation for both operation and flag are very similar, so we can group these two regulations into one.

Summary

Part 121 Domestic and Flag Operations

§121.533(a) and §121.535(a) states that:

Each certificate holder conducting domestic (or flag) operations is responsible for operational control.

The certificate holder is a person or organisation authorized by the FAA  to operate aircraft commercially, maintain aircraft, or conduct training under specific regulations.

In a Part 121 operation, it is most likely an airline operator.

§121.533(b) and §121.535(b) states that:

The pilot in command and the aircraft dispatcher are jointly responsible for the preflight planning, delay, and dispatch release of a flight in compliance with this chapter and operations specifications.

The PIC and aircraft dispatcher are jointly responsible for the preflight planning, delay, and dispatch release. 

§121.533(c) and §121.535(c) states that:

The aircraft dispatcher is responsible for—

(1) Monitoring the progress of each flight;

(2) Issuing necessary information for the safety of the flight; and

(3) Cancelling or redispatching a flight if, in his opinion or the opinion of the pilot in command, the flight cannot operate or continue to operate safely as planned or released.

1. Monitoring
   • Must be able to follow the entire duration of the flight
2. Issuing
   • Issue to the PIC any information that may affect the safety of the flight, such as weather, traffic delays, or NOTAMs.
3. Cancelling or redispatching
   • If in the opinion of the PIC or ADX, you are able to cancel or re-dispatch a flight if the flight cannot operate due to safety. For example, delaying due to weather, or cancelling due to an accident at the destination airport.

§121.533(d,e) and §121.535(d,e) states that:

(d) Each pilot in command of an aircraft is, during flight time, in command of the aircraft and crew and is responsible for the safety of the passengers, crewmembers, cargo, and airplane.

(e) Each pilot in command has full control and authority in the operation of the aircraft, without limitation, over other crewmembers and their duties during flight time, whether or not he holds valid certificates authorizing him to perform the duties of those crewmembers.

Each certificate holder conducting supplemental operations—

The pilot in command and the director of operations are jointly responsible for the initiation, continuation, diversion, and termination of a flight in compliance with this chapter and the operations specifications. The director of operations may delegate the functions for the initiation, continuation, diversion, and termination of a flight but he may not delegate the responsibility for those functions.

The director of operations is responsible for cancelling, diverting, or delaying a flight if in his opinion or the opinion of the pilot in command the flight cannot operate or continue to operate safely as planned or released. The director of operations is responsible for assuring that each flight is monitored with respect to at least the following: