Extended Twin Operations (ETOPS)
Extended Twin Operations (ETOPS) or Extended Operations describes an aerial maneuver in which a twin-engine aircraft is able to extend its flight away from emergency landing fields. ETOPS modifies the standard for twin-engine flights, which is to remain no further than 60 minutes (flying time) from a viable landing zone at any given time. ETOPS typically take place where landing is impossible, such as long oceanic flights, or during flights over areas with few regional airfields.
ETOPS have previously been restricted by FAR Part 121.161, which places restrictions on air carriers over certain routes; ETOPS is an added privilege or an exemption from the stated rule imposed by the FAA outlined in FAR Part 121.161 (see below).
In AC-120-42B, the FAA defines ETOPS as:
"An airplane flight operation during which a portion of the flight is conducted beyond 60 minutes from an adequate airport for turbine-engine-powered airplanes with two engines, and beyond 180 minutes for turbine-engine-powered passenger-carrying airplanes with more than two engines. This distance is determined using an approved one-engine inoperative cruise speed under standard atmospheric conditions in still air.In a nutshell, ETOPS came about as a result of FAR Part 121.161 in order to allow aircraft to fly routes that would otherwise be against the regulations per Part 121."
CFR Part 121.161
Specifically, CFR Part 121.161 states the following:
"…no certificate holder may operate a turbine-powered aircraft over a route that contains a point: At first, the acronym ETOPS was used to describe only Part 121 aircraft with two engines. Since its inception, the ETOPS regulations have been expanded to include any two-, three-, or four-engine aircraft carrying passengers for hire over an area in which airports are not accessible per the FAA's regulations, hence the acronym change from "extended twin operations" to just "extended operations."
Carriers using twin-engine aircraft can apply for ETOPS certification in any of the following categories, according to AC-120-42B:
- 75-minute ETOPS
- 90-minute ETOPS
- 120-minute ETOPS
- 138-minute ETOPS
- 180-minute ETOPS
- 207-minute ETOPS
- 240-minute ETOPS (for a specific geographical area)
- 240+minute ETOPS (based on specific city pairs)
Beginning in 1936, a pilot or operator had to prove that there were suitable landing fields at least every 100 miles along their route. When CFR Part 121.161 was established in 1953, aircraft operators had to ensure a landing area within 60 minutes of their route. With three- and four-engine aircraft, the rules continued to change to keep operators flying efficiently while maintaining a safety net for aircraft should an engine fail.
The first ETOPS approval was given to Trans World Airlines in 1985, the same year the Federal Aviation Administration began allowing twin-engine aircraft an extension to a 120-minute diversion period. It was then extended even further to the 180-minute maximum in 1988.
Today, an ETOPS rule of 240 minutes is approved in certain circumstances for three and four-engine jets. Boeing was the first to obtain ETOPS-240 certification for its Boeing 777 aircraft.