How Flying Works
What Happens If an Engine Fails Mid-Flight?
Until the mid-1980s, a twin-engine airliner simply couldn’t fly you across the Atlantic. A rule from 1953 said any twin had to stay within 60 minutes of a diversion airport, flying at single-engine speed, at all times. That made ocean crossings on two engines almost impossible, and left long-haul flying to three- and four-engine aircraft for three decades. The regulation that finally changed this was ETOPS, officially Extended-range Twin-engine Operational Performance Standards. Pilots had their own version: “Engines Turn Or Passengers Swim.”
How a twin-engine jet earned the right to cross an ocean
Trans World Airlines received the first real ETOPS-120 certification for its Boeing 767 fleet in 1985, allowing 767s to fly transatlantic routes on two engines for the first time. It changed the shape of the industry faster than almost anyone expected. The 767 went on to become one of the most common aircraft on North Atlantic routes. The economics were simply better on two engines than four, and once the safety case was proven, airlines moved fast.
What the number in an ETOPS rating actually means
The number is in minutes, and it sets how far from a diversion airport the aircraft may fly. An airline and aircraft certified for ETOPS-180 can fly routes where the plane is never more than 180 minutes from a suitable diversion airport on one engine, at a lower speed and height if needed. Ratings run from ETOPS-120 through 180 and 240, and now to 330 minutes and beyond (up to 370 on the A350) on the newest widebodies. Those figures let a twin-engine 787 or A350 fly routes that once needed four engines, including ocean and polar crossings. Mentour Pilot’s “Taming the Twin” series breaks down engine failure during takeoff, in cruise and in bad weather, because this scenario is so widely misunderstood. A twin losing an engine mid-flight isn’t a countdown to disaster. The aircraft, the route and the crew are all certified and trained to handle it calmly, for hours if necessary.
Try it
ETOPS: how far from an airport may a twin jet fly?
Each circle shows how far the aircraft could fly on one engine within the time limit (about 400 knots in still air here). The flight must stay inside the circles. At 60 minutes the direct New York–London great circle leaves the circles in mid-Atlantic, which is why early twin jets had to fly long detours or weren’t allowed at all. With a 120 or 180-minute ETOPS rating the gap closes. Circles are approximate.
The sequence
An engine failure, from detection to landing
Engine failure detected
Cockpit alerts and instrument indications; the crew immediately identifies and confirms which engine.
Memory items & checklist
Pilots run trained memory items first, then the full checklist — securing the failed engine, managing thrust and configuration on the remaining engine(s).
Divert decision
Crew selects the nearest suitable airport within the aircraft's certified ETOPS diversion time, factoring weather, runway length and fuel.
Single-engine cruise/descent
up to ETOPS limitThe aircraft is fully capable of maintaining safe altitude on the remaining engine for the certified diversion window.
Landing at diversion airport
A normal, if unplanned, landing — emergency services are typically on standby as routine precaution, not because of any expectation of an accident.
The jet that was cleared for 370 minutes before it flew a passenger
Most twinjets earned longer ETOPS times step by step, proving their engines in service first. The Airbus A350 broke that pattern.
On 16 October 2014, before the first aircraft was even delivered, EASA approved the A350-900 for ETOPS beyond 180 minutes. An option let operators choose up to 370 minutes. Six hours and ten minutes from the nearest suitable airport, on one engine, at the approved speed.
That approval rested on years of data from earlier twins and on the design itself: systems with built-in redundancy, fire suppression sized for the longest diversion, and engines whose reliability could be shown in testing.
What 370 minutes opens up is geography. Routes over the far South Pacific and the Southern Ocean, where airports are thousands of kilometres apart, become legal for a twin. Not every airline pays for the top rating. It means extra maintenance and training, so many choose 180 or 300 minutes to match the routes they actually fly.
Sources & Further Reading
Common Questions
Frequently Asked Questions
Can a twin-engine plane really fly on just one engine?
Yes, with room to spare. A single modern high-bypass turbofan makes enough thrust on its own to hold a safe altitude and reach a suitable airport. Proving that in advance is exactly what every twin-engine ETOPS certification is for.
What does an ETOPS rating like “ETOPS-180” mean?
The number is minutes: ETOPS-180 means the aircraft and airline are certified to fly routes where the aircraft is never more than 180 minutes from a suitable diversion airport on one engine. Ratings run from ETOPS-120 up to 330 on the 777 and 787 and a 370-minute option on the Airbus A350, which is what makes long ocean and polar routings viable for twinjets today.
Why did four-engine aircraft dominate long-haul flying for so long?
Before ETOPS, a 1953 rule kept twin-engine airliners within 60 minutes of a diversion airport at single-engine speed. In practice that barred them from ocean crossings. Four-engine aircraft like the 747 had no such limit, which is why they, not twins, ruled long-haul flying for three decades.
Is losing an engine actually rare?
Very. Modern turbofans shut down in flight only a handful of times per million engine flight hours. Engine failure is one of the most drilled scenarios in pilot training precisely because it’s so rare in real life that crews need regular simulator practice to stay sharp.
Last reviewed: October 2026. Facts that change, such as fleets, airspace and airline ownership, are re-checked on a schedule. Spotted an error? Email contact@skyplus.news and we’ll fix it. See how we check facts.