How Flying Works
What Happens If an Engine Fails Mid-Flight?
Until the mid-1980s, a twin-engine airliner simply could not fly you across the Atlantic. A rule dating to 1953 required any twin-engine aircraft to stay within 60 minutes of a diversion airport, flying at single-engine speed, at all times — a restriction that made ocean crossings on two engines essentially impossible and handed long-haul flying entirely to three- and four-engine aircraft for three decades. Pilots had their own nickname for the eventual regulation that changed this: ETOPS, officially Extended-range Twin-engine Operational Performance Standards, unofficially “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. By 1991, more passengers were crossing the Atlantic aboard 767s than aboard all three- and four-engine aircraft combined, a genuine first in aviation history. By 2000, more than half of all transatlantic crossings were being flown by the 767 family alone. 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 minutes, and it defines exactly how far from a diversion airport the aircraft is allowed to fly. An airline and aircraft certified for ETOPS-180 can operate routes where the aircraft is never more than 180 minutes from a suitable diversion airport, flying on one engine, at reduced speed and altitude if necessary. Ratings scale from ETOPS-120 through 180, 240, and now past 330 minutes on the newest widebodies — figures that make a twin-engine 787 or A350 viable on routes that once genuinely required a four-engine aircraft, including transoceanic and polar routings. Mentour Pilot's “Taming the Twin” series — separate, detailed breakdowns of engine failure during takeoff, during cruise, and in poor weather — exists precisely because this scenario is so widely misunderstood: a twin-engine airliner losing one engine mid-flight is not a crisis with a ticking clock to disaster. It's a scenario the entire aircraft, route and crew are specifically certified and trained to handle, calmly, for hours if necessary.
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.
Sources & Further Reading
Common Questions
Frequently Asked Questions
Can a twin-engine plane really fly on just one engine?
Yes, and not just barely — a single modern high-bypass turbofan produces enough thrust on its own to maintain safe altitude and continue to a suitable airport, which is exactly what every twin-engine ETOPS certification exists to prove in advance.
What does an ETOPS rating like "ETOPS-180" actually 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 through ETOPS-370 and beyond on the newest widebodies, which is what makes routes like the Pacific "Island Hopper" or long 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 — effectively barring them from ocean crossings entirely. Four-engine aircraft like the 747 had no such restriction, which is why they, not twins, defined long-haul flying for three decades.
Is losing an engine actually rare?
Very. Modern turbofan in-flight shutdown rates are measured in single-digit events per million engine flight hours — engine failure is one of the most thoroughly drilled scenarios in pilot training specifically because it's so uncommon in real operations that crews need deliberate simulator practice to stay sharp on it.