Federal Aviation Regulation (FAR) 121.161 states “Unless authorized by the administrator, based on the character of the terrain, the kind of operation, or the performance of the airplane to be used, no certificate holder may operate two-engine airplanes over a route that contains a point farther than 1 hour flying time (in still air at normal cruising speed with one engine inoperative) from an adequate airport.” The rule was written in the days of the propliner when piston engines didn’t have the reliability of modern jet turbines. When the Boeing 767-200ER entered service, it was the first commercial twin-jet capable of crossing the oceans*- when Boeing’s director of engineering, Dick Taylor, first approached FAA administrator Lyn Helms in 1980, Helms responded “It’ll be a cold day in hell before I let twins fly long haul, overwater routes.” Helms even felt that the 60-minute rule was too generous. Despite his opposition, though, in 1982, the FAA began technical discussions with aircraft manufacturers, airlines and ICAO (they had formed a study group of their own in 1982) on the possibility of extended twin-engine overwater flights. At an ICAO meeting in Montreal that December, the FAA asked airline operators of twin jet aircraft to compile a database of inflight events and engine shut downs. Since long range commercial twins were relatively new to the market, the FAA needed a database to draw upon in figuring out the regulatory details of what would become ETOPS flying. After the Air Canada Flight 143 incident (the “Gimli Glider) where fuel starvation resulted in a skillful emergency landing on an old Canadian military air strip, some thought it a set back for what Dick Taylor had been pushing for with the Boeing 767. However, in a speech to the Royal Aeronautical Society in London in late 1983, he argued that fuel starvation would have shut down all the engines regardless of whether you have two, three, or four engines.
In 1980 three- and four-engined aircraft handled all the long range routes, particularly those that were overwater. There was a joke that stated “” But modern technology and computerized systems brought to the Boeing 767 a level of redundancy, safety, and efficiency not seen in any prior commercial aircraft. And it wasn’t just the reliability of the engines, the various systems of the 767 facilitated the development of ETOPS- Extended-range Twin-engine Operational Performance Standards- the ability of a twin engine jetliner to exceed the old 60-minute rule.
On 1 February 1985, TWA Flight 810 departed Boston for Paris on the first revenue passenger flight in history under the 120-minute ETOPS rule. The new ETOPS rule shortened the flight distance and it would replace a Lockheed L-1011 Tristar that normally served the route. Before Flight 810 departed, sixteen TWA pilots went through specialized ETOPS training on international requirements, intensive time in a simulator and landing procedures for the airport at Sondrestromfjord in Greenland, the designated 120-minute diversion airport. Eleven observers from the FAA were aboard TWA 810 and the fuel burn was found to be 7,000 lbs an hour less than that of the L-1011 Tristar on the same route. TWA was so convinced of the efficiency of the 767 with the 120-minute ETOPS rule that it spent $2.6 million per aircraft retrofitting all of its 767-200s for 120-minute ETOPS compliance.