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Extended Range Operations with Twin-engine airplanes (ETOPS)

ETOPS  – Extended Range Operations with Twin-engine airplanes: An airplane flight operation during which a portion of the flight is conducted beyond 60  minutes and up to 180 minutes from an adequate airport for turbine-engine-powered airplanes with two engines.  

This distance is determined using an approved one-engine inoperative cruise speed under standard atmospheric conditions in still air.

As a prerequisite to obtaining any operational approval, the certificate holder must show that an acceptable level of propulsion system reliability has been achieved in service by the world fleet for that particular airplane-engine combination. The candidate certificate holder also should obtain sufficient maintenance and operation familiarity with the particular airplane-engine combination. Each certificate holder requesting approval to conduct ETOPS by the in-service method should have operational experience appropriate to the operation proposed.

The Boeing 767  was the first  Aircraft certified for ETOPS. TWA received an ETOPS rating for Boeing 767 service between St. Louis and Frankfurt, allowing TWA to fly its aircraft up to 90 minutes away from the nearest airfield. Later  the rating was extended to 120 Minutes.

The 767 was the first ETOPS Aircraft

The 767 was the first ETOPS Aircraft

FAA guidance material regarding the operation of twin-engine airplanes for extended periods beyond alternate airports may be found in (AC 120-42B) Extended Operations (ETOPS and Polar Operations) 


a. All two-engine airplanes and three- and four-engine passenger-carrying airplanes operated under part 121 are required to comply with 14 CFR 121.161. This regulation imposes special requirements for ETOPS for these airplanes. These operations are defined as:

(1) Two-Engine Airplanes. These are flights whose planned routing contains a point farther than 60 minutes flying time from an adequate airport at an approved one-engine inoperative cruise speed under standard conditions in still air.

(2) Passenger-Carrying Airplanes with More Than Two Engines. These are flights whose planned routing contains a point farther than 180 minutes flying time from an adequate airport at an approved one-engine inoperative cruise speed under standard conditions in still air.

b. To conduct ETOPS, the specified airplane-engine combination must be certificated to the airworthiness standards of transport-category airplanes and be approved for ETOPS. Airplane certification guidance for ETOPS can be found in 14 CFR  121.162 and 25.1535. As with all other operations, a certificate holder requesting any route approval must first show that it is able to satisfactorily conduct operations between each required airport as defined for that route or route segment, and any required en route alternate airport. Certificate holders must show that the facilities and services specified in 14 CFR  121.97 through 121.107 (domestic and flag operations) and 14 CFR 121.113 through 121.127 (supplemental and commercial operations) are available and adequate for the proposed operation. In addition, the certificate holder must be approved for ETOPS under part 121.


a. Section 121.161 has an extensive historical basis, which began as early as 1936. Before obtaining approval for operation in 1936, an applicant operating an airplane with two piston engines were required to show that intermediate fields available for safe takeoffs and landings were located at least at 100-mile intervals along the proposed route. In 1953, 14 CFR  121.161 imposed the 60-minute rule on two- and three-engine airplanes. In 1964, three-engine airplanes were exempted, leaving the restrictions only on two-engine airplanes based on the lack of satisfactory engine reliability in the operation. In response to improvements in engine design and reliability, and responding to the needs of industry, the FAA has provided guidance for deviations from the rule that have allowed two-engine operations to expand incrementally beyond the initial 60-minute restriction. Currently, engine reliability has improved to a level where the safety of the operations is not impacted so much by the number of engines, but by other factors that affect operations of all airplanes whose routings take them great distances from adequate airports. Throughout the evolution of the current 14 CFR  121.161, the following factors have remained constant:

(1) The rule has always applied to all areas of operation, and has not been limited to overwater operations.

(2) Any additional restrictions imposed or, alternatively, any deviations granted to operate in excess of the basic requirements, were based on a finding by the Administrator that adequate safety would be provided in the proposed operation and current levels of safety would be maintained when all factors were considered. This finding was never limited to engine reliability alone.

(3) The airports used in meeting the provisions of the rule must be adequate for the airplane used (that is, available for safe landings and takeoff with the weights authorized).

(4) Adequate levels of safety within the operation are to be maintained. Operations over increasingly remote areas and the possibility of increased diversion lengths have a potentially negative impact on the safety of the diversion, and thus the operation as a whole. Additional regulatory requirements are intended to ensure that this potential increase in risk is mitigated and that adequate levels of safety within operations are retained.

(5) When considering the impact of operating at greater distances from airports, the certificate holder must show that the operation can be conducted at a level of reliability that maintains an acceptable level of risk.

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