Nothing excites a statistician’s heart quite like morbidity. After all, people might not care much for numbers in most things, but if there is chance it might kill you, people tend to listen. And airline safety is hardly a fringe topic. It has been covered extensively in the news, particularly after high profile events such as the disappearance of MH370 over the Indian Ocean, and the downing of MH17 in eastern Ukraine (Malaysia Airlines did not have a good year in 2014). So how do we quantify airplane safety?
A straightforward way to look at it, is simply to count the number of airplane crashes that resulted in at least one fatality. We will include all commercial flights, both national and international that carried passengers. This means looking at both the big airline brands, but also the more accident-prone firms flying small turboprop planes. We will exclude cargo, rescue and military flights, as they operate under very different conditions, and are arguably not relevant to the vast majority of air travellers. On the other hand, we will include any cause for the crash, both accidental (e.g. engine failure) and intentional (e.g. military action) resulting in loss of life, as long as the affected airplane is on a commercial flight.
Fortunately, commercial airline accidents are pretty rare. In 2017 there were just 5 accidents that meet our criteria, with a total of 13 casualties. In fact, 2017 was the safest year on record for commercial airlines. However, it seems unfair to judge airline safety based on performance in a single year, since accidents are so rare. Equally, it would be unfair to judge an airline today by their record in the 1970s and 80s, a time when airplane crashes were more common, and many modern carriers didn’t exist yet. Instead, we can look at a 20-year window (1997-2017) to get an idea of the relative safety of different airlines.
As you can see, not one airline has a monopoly on airplane crashes. Most airlines on the list have suffered one or two deadly crashes, with the largest number being 3 for Hageland Aviation Services, a medium-sized provider operating out of Anchorage, Alaska. Many big names such as Delta, Lufthansa or KLM have not suffered a crash leading to fatalities in the last 20 years.
Perhaps more interestingly, we can consider how many crashes airlines experience in relation to their operation size. If an airline operates many flights a year, we would expect an accident to occur eventually. Equally, if an airline operates few flights but experiences a large number of crashes, that is cause for concern. To simplify the process, we will only consider airlines that have experienced two or more crashes in the last 20 years. The number of flights operated are difficult to ascertain, and is a number that fluctuates from year to year. Instead, we will take the fleet size – that is, the number of airplanes registered to a given airline – at the most recent time of operation, and compare it to the number of crashes it has experienced.
it is evident from the data that there is no relation between fleet size and the number of crashes. We have very small operations such as Karibu Airways with a single plane, all the way to Malaysia Airlines, one of the largest operators in the world with 71 aircraft in operation.
So far, we have looked at the frequency of crashes, but what if we looked at the deadliness of crashes? Do any airlines stand out?
Here the size and colour correlate with the total number of fatalities across all crashes for that airline in the 20-year window. One clear stand-out is Malaysia Airlines. The two crashes we mentioned above, MH370 and MH17, make up a total of 537 casualties, which is by far the largest loss of life in commercial aviation in the past two decades. Both Air France (in 2009) and Metrojet (in 2015) suffered crashes leading to the loss of 228 and 224 people, respectively. Interestingly, there is no clear relationship between fatalities and airline – not by fleet size, geography, or other indicators.
While we might be tempted to interpret these data as nudging us not to fly with one airline or another, the truth is that airplane accidents are thankfully so rare that is difficult to determine how risk factors may vary, if at all, from one airline to another. However, we can still make one more assessment – if we were to experience an airplane crash with one of these companies, how likely are we to walk out alive? We can quantify this by using this simple formula to calculate a survivability rating:
1 – (fatalities / people on board)Where a value approaching 0 means most people on board perished, while a value approaching 1 means most people on board survived.
First, some bad news. Most airplane crashes that result in a fatality tend to be bad. Of the 220 crashes involving at least one fatality in the last 20 years, 128 of them resulted in the death of all passengers and crew members. The average survivability of crash is 0.24, meaning on average, only around 24% of people on board survived. The good news is that there are a few airlines with lucky breaks; Asiana and Dagestan Airlines for example, both experienced emergencies with large numbers of passengers (100+) and managed to land with few casualties. Of course, there are many airplane accidents that do not result in fatalities, but of those who do, these are the lucky ones.
As a final point, it is worth stressing that air travel remains, on average, an extremely safe method of transport. While every single of these deaths is a tragedy, a total of 5,979 deaths in worldwide commercial aviation deaths over 20 years, or around 300 per year, is a tiny amount. You are over twice as likely to die cycling in the United States (818 fatalities in 2015) or around 4000 times more likely to die in a road traffic accident worldwide (estimated at 1.25 million deaths in 2013). So continue flying, and rest assured that no matter which airline you choose, you are using probably the safest method of transport.
—————————————————————————————————
Airplane accident data from planecrashinfo.com and dot cluster illustration made with RAW Graphs.
An honourable mention is due to an intoxicated man who, on the 11th June 2012, stole a Antonov AN-2 and crashed it near Serov, Russia. Official cause of accident: Illegal Flight.
This article was originally published on 28 February 2018.