Monday, October 1, 2018

Which airlines are the best?

Scientists are known to get about a bit. They attend conferences and give workshops, they go on sabbatical, and sometimes they even have holidays. Many of these activities require them to be in other places than their home city; and to get there they often resort to air travel. This makes it of interest to them to know which airlines are considered to be "good". Scientists may not have much choice about which airlines they can choose to fly, depending on where they live, but they can at least try to fly on one of the good ones.

They are not alone in this desire, and so inevitably there are web sites that provide the necessary information. These include AirHelp Airline Worldwide Rankings; but the best-known listing is the annual one from Skytrax, a UK-based consumer aviation agency.

Each year, Skytrax conducts a survey in which "airline customers around the world" vote for the best airline. The survey results are released at the beginning of each year, and they thus refer to the previous year's survey. Skytrax note that "over 275 airlines were featured in the [current] customer survey but we only feature the top 100 listing."

The Skytrax top-100 data currently exist online for the years 2012-2018 inclusive, which cover the years 2011-2017. It can be useful to consider data for multiple years, because some airlines have greatly improved their ranking through time, while others have slipped back. There are 80 airlines with top-100 data for each of the years 2011-2017, and another 45 airlines that have appeared in the top 100 at least once. A few airlines have also merged during these years.

We can explore the multi-year data for the 80 airlines using a network analysis, to visualize the overall pattern. I first calculated the Manhattan distances pairwise between the airlines, and then plotted these using a NeighborNet graph, as shown in the figure below. Airlines that have similar rankings across the years are near each other in the network; and the further apart they are in the network then the more different are their overall rankings.

As you can see, this is pretty much a linear network, with the best-ranked airlines at the top-right, and then continuing down to the bottom-left. A simple list of the average rankings across the years would be almost as informative. In particular, the top-ranked airlines have remained at the top across the years; and it is only in the middle and especially at the bottom that there has been movement among the rankings (that is, the network broadens out at one spot in the middle and then again at the end).

Note that the top end of the list consists mainly of airlines from the Middle East and Asia. Australia has only two airlines, both of which do well in the network, along with the only one from New Zealand. The presence near the top of both Turkish Airlines and Garuda Indonesia may surprise some people.

You will also note that the US airlines are generally closer to the bottom of the network — they are marked in red in the network. The airlines from China are mostly there, also (except Hainan Airlines). It is not a coincidence that neither of the world's two biggest economies runs a high-quality airline. It seems that the only way to do this is actually to rely on government subsidies, which is how most of the top-ranked airlines are doing it.

Finally, there are few discount airlines that make it into the top 50. Put simply, the economics of running an all-economy-class plane do not allow much in the way of customer service (see How Budget Airlines Work). It is actually the first-class and business-class passengers on any given plane that allow it to take off at all, in terms of making money for the airline — a classic example of the 80/20 rule: 80% of the money comes from 20% of the passengers (see The Economics of Airline Class).

Finally, in a similar vein, you could also contemplate the sites pertaining to airport quality (eg. AirHelp Airport Worldwide Rankings, World Airport Awards), as well as the Guide to Sleeping in Airports. There are also sites that tell you which seats to choose in any given plane (eg. SeatGuru).

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