"What if an engine stops?" It's one of the biggest fears I hear from nervous flyers, and it's a completely reasonable question. Engines feel like the thing holding the aircraft up. So let me explain, plainly and honestly, what really happens.
The short answer
Every twin-engine airliner is designed and certified to fly safely on one engine. Not just to limp along, but to take off, climb, cruise, and land on a single engine. Engine failure is something pilots train for again and again, and it's one of the most rehearsed situations in aviation.
Engines are remarkably reliable
Modern jet engines are among the most reliable machines ever built. Engine failures in flight are rare enough that many airline pilots go through their whole careers without experiencing a real one outside the simulator. Engines are monitored continuously by onboard systems and on the ground, and maintenance is based on detailed data about how each engine is performing.
The reliability of twin engines is so well proven that regulators allow twin-engine aircraft to fly long routes over oceans and remote areas, a set of rules known as ETOPS (Extended-range Twin-engine Operational Performance Standards). Under these rules, the aircraft must always be within a set flying time of a suitable airport on one engine. You can read the US rules in the FAA's guidance on >ETOPS.
Designed for one engine from day one
When engineers design an airliner, they don't assume both engines will always be running. They design it so that one engine alone can handle the most demanding situation: an engine failure at the worst possible moment during take-off.
That's why, before every flight, we calculate our take-off performance with an engine failure in mind. The numbers tell us the speed at which we can safely stop on the runway if something goes wrong (called V1), and confirm that if an engine fails after V1, we can safely continue the take-off on the remaining engine and climb clear of obstacles. Every take-off is planned with that margin built in.
What pilots do if an engine fails
We train for this in full-motion simulators regularly. The simulator is so realistic that it moves, shakes and sounds like the real aircraft. Here's a simplified version of the routine.
1. Fly the aircraft. The first rule in aviation is always "aviate, navigate, communicate." One pilot focuses entirely on flying the aircraft safely.
2. Identify the problem. The aircraft's displays tell us clearly which engine is affected and what's happening.
3. Run the procedure. We follow a checklist that we've practised many times. It might involve trying to restart the engine or securing it.
4. Communicate. We tell air traffic control, who will give us priority and help. We brief the cabin crew and make an announcement to passengers.
5. Plan the landing. Depending on where we are, we might return to the departure airport or divert to a suitable nearby one. On one engine, the aircraft handles well, and landings are routine for trained crews.
You might notice the aircraft's sound changes and the aircraft may yaw slightly (swing sideways) until the pilots trim it out. The cabin will stay pressurised and powered. Many passengers barely notice anything.
What about the sound of a bang or flames?
Sometimes an engine problem can produce a loud bang, which can be alarming. One common cause is a compressor stall (also called a surge), where the airflow through the engine is briefly disrupted. It can be loud and may even produce a visible flash, but it's often momentary and the engine may recover on its own. If not, pilots follow their procedures. Engines are designed to contain failures, and each one has fire detection and extinguishing systems.
What if both engines fail?
This is extremely rare. But even in this case, an airliner doesn't fall out of the sky. It becomes a glider. A typical airliner can glide a long way, roughly 15 to 20 kilometres for every kilometre of height (around 2 to 3 nautical miles per 1,000 feet). From cruising altitude, that means well over 150 km of gliding distance, giving pilots time to attempt engine restarts and plan a landing.
The aircraft still has electrical and hydraulic power from backup systems, including a small wind-driven turbine called the RAT (ram air turbine), which drops out into the airflow to provide emergency power. Pilots practise these scenarios too.
Why there's more than one of everything
Aviation is built on a principle called redundancy. Critical systems are duplicated, or even triplicated. Most airliners have multiple hydraulic systems, multiple electrical generators, backup batteries, more than one flight computer, and two pilots. The design philosophy is that no single failure should lead to an unsafe situation.
Engines are a good example. Two engines, each capable of flying the aircraft alone, plus an APU in the tail that can provide electrical power and air if needed.
How pilots train
Airline pilots go through recurrent training and checks in simulators at regular intervals, typically every six months. Engine failures, especially at take-off, are among the most commonly practised scenarios. We don't just learn the procedure once. We practise it until it's second nature, and we're tested on it.
I've practised engine failures more times than I can count across turboprops, narrowbody and widebody jets. Every type is different, but the principles are the same, and the training is thorough. When pilots talk about engine failures, we talk about them calmly, because to us they are a known, rehearsed situation with a clear plan.
What you might hear on board
If there's an engine issue, you might hear: - A change in engine sound or a period of quieter flight. - An announcement from the flight deck explaining that we're returning or diverting "as a precaution." - Emergency vehicles waiting at the airport on landing. This is standard precaution, not a sign of danger.
It's worth noting that a "precautionary return" is often exactly that: a cautious decision because an indication needs checking. Pilots and airlines take a conservative approach. That's a good thing.
Putting the fear in perspective
The fear of an engine failure is usually a fear of something unknown and uncontrollable. In reality, it's well-known and well-controlled. Aircraft are designed for it, pilots train for it, and procedures are tested and refined over decades of experience.
If you'd like to understand the bigger safety picture, read how safe is flying, by the numbers. And if the sound of the engines changing after take-off worries you, my guide to every normal noise on a plane explains why the engines get quieter a minute after lift-off (it's planned, not a failure).
The captain's bottom line
Your aircraft is designed to fly safely on one engine. Your pilots have practised exactly that situation many times in simulators that feel like the real thing. Engines are extraordinarily reliable to begin with. An engine problem is rare, manageable and rehearsed. That's not a reassuring story we tell passengers. It's simply how airliners are built and how pilots are trained.
Want this in your pocket?
Download my free illustrated PDF, Turbulence & Aircraft Sounds Explained by an Airline Captain, and take it on your next flight.
Get the free guideFrequently asked questions
Can a plane fly with one engine?
Yes. Every twin-engine airliner is certified to take off, climb, cruise and land safely on one engine. It is a core part of aircraft design and certification.
What happens if both engines fail?
It is extremely rare. An airliner does not fall out of the sky; it becomes a glider and can cover a long distance while pilots attempt restarts and plan a landing. Pilots train for this too.
How often do pilots practise engine failures?
Airline pilots practise engine failures in full-motion simulators during regular recurrent training, typically several times a year, including at the most demanding moment: just after take-off.
This article is general information, not medical or professional advice. Always follow instructions from your crew. If fear of flying seriously affects your life, please speak to a doctor or qualified therapist.
