A sunny day, 29 degrees, a gentle north-westerly breeze: flying conditions were near perfect as Qantas flight 520 began rolling down the runway at Sydney Airport en route to Brisbane. This particular plane, a Boeing 737-800, had been delivered new to the national carrier in November 2005 and given the tail number VH-VYH. A dependable workhorse, it had scooted up and down Australia’s east coast, mostly, for 19 years without notable incident.

On this day, November 8, 2024, the Boeing had already made three trips, the first a breakfast run out of Sydney just before 7am. It was now setting off for the return leg to Brisbane. QF520 left the gate around 12.15pm and taxied to its slot in the take-off line-up, from where it was given the go-ahead. Its pilots hit the gas and the engines bellowed. It soon reached 200km/h and passed what aviators call “V1”: the point at which a plane is travelling too quickly to safely abort take-off.

Exactly what happened next is now in the hands of safety investigators. What we do know is that, as the 737 was still gathering speed down the runway, one of its two engines suddenly destroyed itself. It failed, spitting fragments of superheated metal out of its exhaust chute, which shot to the ground, sparking a grassfire that soon made TV news.

Some 40 per cent of air travellers report some fear of flying. Yet air travel is by far the safest form of transport, we’re often told. It’s heavily regulated, constantly scrutinised and, in Australia, operated and overseen by thousands of highly trained and dedicated professionals. The statistics confirm it. Australia’s safety record for commercial travel is exemplary: no large jet has ever been lost here. Our oldest airline, Qantas, regularly tops world safety rankings. Yet incidents still happen. Planes bump into each other on the ground. Tyres burst. Turbulence flings people around. Why do things still go wrong, albeit occasionally? Who is responsible for keeping us safe in the air? And what happens when that rarest of event occurs: one of your two engines goes “pop”?

Who keeps us safe in the air?

Flores, a tropical island about an hour’s flight east of Bali, is best known for three things: clear-water scuba diving, komodo dragons that can weigh more than 100 kilograms, and volcanoes, some picturesque and dormant, others not so much. In early November, Lewotobi Laki-laki began erupting in earnest, endangering nearby villages and sending a plume of ash 10 kilometres into the air.

Some 4000 kilometres south, at the Qantas Integrated Operations Centre near Sydney Airport, concern began to build. Famously, all four engines on a British Airways 747 failed after passing through a sulphurous volcanic cloud high above Java in 1982; only after the crew had prepared to ditch in the ocean did the turbofans clear of debris and miraculously restart. Partly as a consequence, when the unpronounceable Icelandic volcano Eyjafjallajökull erupted in 2010, airspace was closed across Europe, which led to some 95,000 flights cancelled and millions of passengers stranded.

As the Flores ash cloud drifted west towards Bali, the Qantas team declared the situation critical and began cancelling flights into Denpasar for both Qantas and its subsidiary Jetstar. On the day we visit the operations centre, the crisis management team is about to meet in its purpose-built war room to gauge when flights might be allowed to resume. “It’s about determining when it’s going to be safe for us to operate,” says Qantas’s head of safety, Mark Cameron, a former British Airways pilot who knew the 747 crew who survived the volcano in 1982. “Engines do not like breathing in volcanic ash.”

Hundreds of Qantas staff, meanwhile, seated in pods in a vast room at head office, are still scrambling to reschedule flights, alert and mollify annoyed passengers while also dealing with the normal workings of some 100 international and 300 domestic flights on a typical day. For what we’re told is an extraordinarily busy day, though, the atmosphere is hushed and calm: a giant jigsaw puzzle being completed then restarted as mini-crises are discovered and mitigated. Jetstar was doing the same at its operations centre in Melbourne.

The business of air travel is mind-bogglingly complex. But so, too, are the systems underpinning it. They allow it to operate extremely safely, especially compared to any other form of transport.

‘You can’t eliminate risk in any part of your daily life, but our role is to manage the risk to a level at which we’re comfortable that everybody’s going to be safe.’

Mark Cameron, Qantas head of safety

Back in 1944, as World War II saw a flurry of new airports being built, 54 nations including Australia sent delegates to Chicago for a convention that laid the groundwork for international air safety standards. They agreed to create an overarching authority, today called the International Civil Aviation Organization (ICAO), under the auspices of the United Nations to set world standards for airworthiness and maintenance, and airport and airline operations, among other areas. “The aviation industry has an incredibly good safety record,” says Ron Bartsch, an aviation safety expert and founder of Avlaw aviation consulting. “The main reason for that is it’s so strictly and extensively regulated.”

For 2023, ICAO reported the accident rate (such as incidents involving death, injury, aircraft damaged or missing) for commercial aircraft was 1.87 accidents per million departures. To break this down: of 35,250,759 departures, there were 66 accidents, all but one of them non-fatal, the exception a twin-engine propeller aircraft operated by Yeti Airlines that crashed while coming into land at Pokhara in the Himalayas, killing 72 people on board.

The Australian Civil Aviation Safety Authority (CASA) regulates the ongoing airworthiness of aircraft by ensuring airlines adhere to safety standards and a strict maintenance program.Regular maintenance is based on the number of hours the aircraft has flown, or how much time has passed since the last check – different parts require different “periodicity” for being serviced. Engineers could do anything from checking fluids after every flight to replacing wheelpads after a few flights to inspecting or replacing any one of thousands of parts after a specified time.

“What it allows us to do,” says Qantas’s Mark Cameron, “is to be really proactive in how we’re managing risk – because, effectively, that’s what airlines do, we manage risk. We can’t eliminate it because you can’t eliminate risk in any part of your daily life, but our role is to manage the risk to a level at which we’re comfortable that everybody’s going to be safe.”

At Qantas HQ, various teams plan virtually every aspect of each flight: checking the weather; working out the best route (from several options if flying overseas, including avoiding volcanic eruptions or geopolitical hazards such as closed airspace in the Middle East, which Qantas has been navigating since early August); making sure cargo is loaded correctly so the plane is balanced; identifying dangerous goods on board; and screening for troublesome passengers on the banned “no fly” list … and on it goes.

With all that in place, the pilots run pre-flight checks, going over the weather briefing, for example, and any notes on potential dangers. The airline tells pilots how much fuel they need, but the pilot can choose to take more, depending on the possibility of a weather diversion or other delays. The pilot physically walks around the aircraft on the ground to triple-check there are no obvious faults. An engineer will have already signed a certificate of release to service – a legal declaration that the aircraft is fit to fly – before every international flight and at least daily for domestic flights, which the pilot clocks, along with a log of maintenance, before they accept the aircraft for flight.

The pilot’s next contact is with air-traffic controllers, who clear planes for departure according to strict rules that determine “how many aircraft we can have taking off and landing at any one time,” says Airservices Australia’s Michelle Petersen, who is responsible for the towers at all of Australia’s major airports. Controllers also factor in “wake turbulence”, the disruption to the air that a plane leaves in its wake; there needs to be a gap of three minutes between an A380 taking off and a Boeing 737 following it, for example.

All over the world, controllers and pilots speak English and use regulated unambiguous terms: “Qantas one, runway 19 left, cleared for take-off.” Pilots always repeat back the message. “There cannot be any assumptions in the air and we embed safety in everything we do,” says Petersen. The most deadly air disaster in history, which killed 583 people in Tenerife in the Canary Islands in 1977, was blamed, at least in part, on a communication breakdown: two 747s collided on the runway in heavy fog after one tried to take off following a command from air-traffic control that pilots mistook to be an all-clear to depart.

How did plane safety develop?

In the Ancient Greek fable, Icarus was warned by a fledgling aviation regulator (his dad) not to swoop too close to the sea lest his wings, fashioned from feathers and wax, become waterlogged; nor should he fly too close to the sun in case the wax melted. In other words, the operational envelope of his equipment was well understood and his fate (a fatal wax-feather-decoupling incident) was quite rightly chalked up to pilot error.

Next came 747 ‘jumbos’ – some famously featuring a spiral staircase to an upstairs lounge bar.

Today, aviators talk of jet planes in generations. “Generation one” had panels of dials and gauges and rudimentary autopilots, if any. Think: cars with no airbags or anti-lock braking and possibly alarming handling characteristics, such as the world’s first commercial jet airliner, BOAC’s de Havilland Comet. One, flying from Singapore to London via Bangkok, Rangoon, Calcutta, Karachi, Bahrain, Beirut and Rome in 1954 disintegrated midair, as did two of its sister planes, thanks to structural issues; 23 other Comets, out of 114 in total including prototypes, were lost due to pilot error, design faults and other mishaps.

Next came the beginnings of truly modern jets, including the pretty reliable 747 “jumbos” – some famously featuring a spiral staircase to an upstairs lounge bar – and the first of the Boeing 737s, launched in 1968 and still one of the most-operated airliners today. These had better automatic systems but could still make you think twice about getting on board: the McDonnell Douglas DC-10, in particular, gained a terrible reputation in the 1970s thanks to engine failures and a series of hijackings.

“Generation three” planes saw the introduction of technology such as “terrain avoidance systems”, leading to a rapid reduction in losses that continues today in “generation four” planes, which can “see” all around themselves to take evasive action if something nearby is judged to be on a collision course. Airbus tells us its latest safety systems use real-time data to avoid runway excursions and reduce the risk of landing incidents (“in case the aircraft is too fast, too high or lands too long, an alert will be triggered to advise the crew to perform a go-around or use the maximum reverse and brakes”).

Says Qantas’s Mark Cameron: “If you look at the accident rates throughout that period of time, you just see them plummet across the generations.” Last year was the first to record zero fatalities from commercial jet crashes, despite there being more than 29,000 in service worldwide, according to Boeing’s statistical summary that dates back to 1959. (This excludes turboprop, or propeller, passenger planes such as those operated by Yeti Airlines in Nepal and the ATR-72-500 that crashed over Brazil in August 2024 after stalling and entering a flat spin.)

The age of a plane, meanwhile, says little about how well-maintained it is. “Don’t get confused with cosmetic looks,” says David Evans, a former Qantas pilot of 35 years. “If you walk into an aircraft that looks a bit shabby, the carpet might be a bit threadbare, that has no relationship to its airworthiness.”

“Generation four” planes have a huge number of backups, or redundancies. Those with two engines, such as Boeing 737s, can fly on one. They have multiple alternative power sources. “The A380 had about six different backup systems for wheel brakes. If you’re running out of brakes, you’re having a really bad day,” says Evans. “All of these things have been based around previous incidents … over the 100-odd years of aviation. There are risks every time you go flying, but we mitigate them by … checklists, briefings, plan A, B and C. You’re trying to eliminate surprise.”

There are also at least two pilots on a flight deck at all times, one free to monitor the autopilot while the other scrutinises variables such as fuel consumption and weather. Having said this, airlines and regulators from more than 40 countries have pushed ICAO to help make single-pilot flights safe; the European Union Aviation Safety Agency says such services could start in 2027.

Ron Bartsch doesn’t back such a change. “You need someone who can take the place of the pilot if they have a heart attack or something.” Evans has written in this masthead before that it is an alarming idea, noting that pilots are “the last line of defence”.

What happened with the ‘Max’ planes?

Once in a while, a defect can slip through what the industry calls the “Swiss cheese” safety model. Visualise a packet of Swiss cheese slices, each with holes in different places. For an error to creep through, a hole would have to line up in every slice of cheese. Boeing’s new-ish 737 Max aircraft was delivered to airlines with a fatal flaw: a problem that had managed to pass through every slice of cheese. First, a system that prevented the planes from stalling malfunctioned: perceiving that the planes were climbing too steeply when they were not, it automatically, and repeatedly, forced down the nose. This could, potentially, have been overridden by pilots, had they been trained to recognise the problem – but they had not. As a result, two Max 8 737s crashed – one in Indonesia in October 2018, another in Ethiopia in March 2019 – with the loss of a total of 346 lives.

‘Boeing is still paying the price for the damage to their brand. It’s got a fair way before it regains industry trust.’

It later emerged that Boe­ing had cut corners by updat­ing its now decades-old 737s to the longer, more powerful Max rather than build­ing an entirely new air­craft from scratch, in order to match its chief competitor, the Air­bus A320neo. Max variants were grounded worldwide between March 2019 and December 2020 while investigators determined the cause of the fatal disasters. The groundings, lawsuits and compensation, US Senate investigations subcommittee hearings and cancelled orders kept Boeing’s safety record in the spotlight and have cost the company about $100 billion. Boeing supplied historical safety data for this Explainer but declined an invitation to speak on the record.

Bartsch says the 737 Max troubles have been “a classic example of companies trying to cut costs” ahead of safety. “Boeing is still paying the price for the damage to their brand. It’s got a fair way before it regains industry trust.” Boeing was again in the spotlight earlier this year for its 737 Max aircraft when a Max 9 explosively decompressed above Portland, Oregon after it lost a fuselage panel called a “door plug” that, it turned out, had bolts missing in its installation. Although extremely alarming, there were no serious injuries.

In Australia, CASA has now certified the Max 8 as safe to operate. Virgin, which currently operates eight 737 Max 8 aircraft, requires its pilots to undergo additional training to understand the differences between the new aircraft and previous iterations of the 737. In addition, Boeing has modified the problematic system, called MCAS, so it cannot override a pilot’s ability to control the airplane. “Virgin Australia is one of over 80 airlines operating Boeing 737 Max family aircraft globally,” says Virgin Australia chief operations officer, Stuart Aggs. “More than 1400 of these aircraft are in service around the world, carrying about 700,000 passengers on 5500 flights every day. Over the past 50 years, a journey of continuous improvement has made commercial aviation the world’s safest form of transportation. Virgin Australia retains full confidence in Boeing’s commitment to this journey.”

For all the focus on beleaguered Boeing, Airbus has not been without incident: in September, a Rolls-Royce engine on a Cathay Pacific A350 caught fire and failed, forcing the plane to dump fuel then return to Hong Kong. After inspecting its entire fleet of A350 aircraft, Cathay found that 15 had faulty engine parts that needed to be replaced. A preliminary report into the September incident by Hong Kong’s safety body found a fuel hose had torn, according to Aviation Direct. “This led to a fuel leak, which in combination with oxygen and an ignition source (heat) triggered the fire.”

So, why do accidents still happen?

When the right-side engine failed on Qantas flight 520 out of Sydney just seconds after the “V1″ point of no return during take-off, the pilots knew they had no choice but to keep going and take off with just one power plant. Says David Evans: “V1 is carefully calculated for every takeoff. The only decision pilots have to make prior to V1 is to either stop or go. After V1 there is no decision, you are committed to go flying. Any attempt to stop after V1 will result in a runway overrun.”

The Boeing had been designed for such an eventuality; to take off with just one engine. That did not mean, however, it was routine. Historically, many fatal crashes have occurred at or shortly after take-off, including the disaster in Paris in 2000 that eventually consigned the only supersonic airliner, Concorde, to the history books.

”We spend a fair amount of our career lifetime in simulators, preparing for worst-case scenarios,” says Doug Drury, a former commercial pilot who heads aviation at Central Queensland University. “It’s all about developing these critical skills, thinking, decision-making processes and having good situational awareness.” The Sydney incident was a scenario that pilots regularly simulate in training and their response was by the book, says Mark Cameron, who spoke with them afterwards. “They were saying they really appreciate the training they’d had.”

Their take-off, after the engine had failed, was “low and slow” as the plane crept skywards, circled Sydney airport then landed safely. “Within 15 minutes of the landing, we had the data already available where we could actually see exactly how the crew had flown,” says Cameron. “It was really good in terms of how they controlled the aircraft, recognised the issues, the approach back into Sydney. It’s actually a really good news story for our pilots and systems.”

Passengers who heard the engine go “bang” were alarmed but nobody was injured. Says David Evans: “An engine failure is horrendous from a passenger’s point of view, and even for the cabin crew, but for the pilots it’s a serious inconvenience more than anything. I don’t want to say it’s not a big deal, but it’s not something they haven’t seen many, many times and practised over and over.”

‘We don’t want the engines to fail. But the reality is, there’s always going to be a failure rate. It’s pretty small across the industry.’

So why did this engine give up the ghost? This model is generally very reliable, manufactured since 1997 by CFM International and used in thousands of Boeing and Airbus planes. CFM describes it as “simple and rugged” with a “dispatch reliability” (the rate at which a specific component is held responsible for aircraft delays, turn-backs, diversions, etc) of 99.96 per cent.

Yet nothing is entirely foolproof. CFM engines have failed before, most notably on planes operated by Southwest Airlines in the United States where they shot debris into the fuselage. In 2018, a passenger died after reportedly being sucked out of a window punctured by debris. The US National Transportation Safety Board determined that one of the failed engine’s fan blades had broken off due to fatigue and fractured into fragments. It had likely harboured a tiny crack that had pre-dated a safety inspection, the authority said, “However, the crack was not detected for unknown reasons.”

“We don’t want the engines to fail,” says Cameron. “But the reality is, there’s always going to be a failure rate. It’s pretty small across the industry.” He adds: “An engine failure in itself doesn’t mean you’re going to have an accident because you’ve got trained crew, an aircraft that is certified to fly on one engine and numerous other controls in place.” Doug Drury notes: “Airlines don’t survive if they cut corners. Historically, yes, it’s happened, but in this day and age, post-pandemic, that’s the last thing any airline wants, is to get hit with this.”

In 2010, David Evans was the supervising check captain on QF32, an Airbus A380, when it suffered an uncontained engine failure moments after take-off from Singapore’s Changi Airport en route to Sydney. “Sometimes a failure will have a cascading effect on other systems and QF32 is a good example of that: where an engine exposure created havoc with everything else,” Evans says. The Australian Transport Safety Bureau later found that an oil pipe in the failed Rolls-Royce engine had been manufactured to improper tolerances and had developed a crack due to fatigue, then it leaked oil that caused a fire, which caused a turbine disc to separate from the drive shaft and destroy the engine. The pilots famously landed the plane safely. “You’ll never get rid of risk,” says Evans. “The only thing you can do is mitigate against risk.”

There were 58 uncon­tained (that is, explosive) engine fail­ures on West­ern-built air­craft between 1982 and 2008, according to the US authority the Fed­eral Avi­ation Admin­is­tra­tion – a scary-sounding number until you do the maths: roughly, around one occurrence per 10 million flights per year, or far less likely than being hit by lightning (one in a million).

Some incidents are harder to mitigate than others. Orville Wright was probably the first aviator to hit a bird, in 1905. The most famous bird strike of all was caused by a flock of Canadian geese in 2009, which clogged the engines on an Airbus 320 departing New York and required its captain, Chesley Burnett “Sully” Sullenberger III (later played by Tom Hanks in the movie recreation) to ditch on the Hudson River.

Turbulence, particularly where an aircraft drops suddenly in the absence of any obvious “weather” such as storm clouds – dubbed “clear-air turbulence” – regularly sees flight staff, in particular, injured. A Southwest attendant was scalded by hot coffee in March; a United staffer flung into the air with the drinks cart, then back to the floor, described it as “slamming down from a fifth-floor building”. In May, a passenger died of a suspected heart attack, and more than a hundred were injured, when a Singapore Airlines Boeing 777 suddenly fell nearly two kilometres over three minutes over Myanmar during the breakfast service, one passenger telling the BBC it was “just like going down a vertical rollercoaster”.

‘In an aeroplane, you’re getting all sorts of sensations which you can’t rationalise.’

The incident, while extreme, prompted a round of reminders of the benefits of fastening seatbelts, one of the few aspects of flying that passengers can control. For most “aviophobics”, says Corrie Ackland, clinical director of the Sydney Phobia Clinic, the fear “comes down to this idea that they don’t know what’s happening and they don’t know how to fix it – and those things play up for them”.

News reporting and TV shows put all manner of aviation incidents in the spotlight. “I’ve seen people and their fear is based around what they see on the telly – nothing to do with flying,” says Evans. He helped set up a “fear of flying” program that now partners with Ackland’s clinic where people sit with a pilot in a flight simulator. “In an aeroplane, you’re getting all sorts of sensations which you can’t rationalise,” Evans says. “And there might have been an incident that you were involved in, turbulence perhaps, and noises like the undercarriage retracting or the flaps extending or retracting, and the amygdala [the fight-or-flight centre of the brain] sets off that charge because you think there’s something afoot or something that’s dangerous. But it’s the normal operation of the aircraft.”

A week after landing in Sydney, meanwhile, the Qantas Boeing 737 that suffered engine failure was back in the air. With a new powerplant, VH-VYH shuttled once again from Sydney to Brisbane to Sydney to Melbourne to Brisbane. The damaged engine would be scrutinised to determine what, exactly, had happened, and what remedies might be put in place to minimise the chances of it happening again.

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