After an unexpected natural disaster in 2010 forced the closure of airspace above some 20 European countries and caused unprecedented global flight disruption, researchers set out to find out just how vulnerable the worldwide airline network really is.
The 2010 incident was caused by the eruption of the Icelandic volcano Eyjafjallajökull, which spewed dust and ash in the millions-of-tons into the atmosphere above northern and western Europe, and threatened to clog airline jet engines. In the five days after 60 percent of European flights were cancelled, grounding more than 100,000 passengers.
Inspired by the incident, Trivik Verma of the science, engineering and technology-focused ETH Zurich university and a team of researchers looked at the global airline network and found a core of major, robust air travel hubs with alternate routes.
They also found, unexpectedly, “another network of peripheral airports that are hugely vulnerable,” underneath the primary hubs, MIT Technology Review reports. When disconnected from the global grid, these closed hubs leave entire sections of the planet cut off from the fastest, primary mode of modern global transportation.
After analyzing 18,000 routes between 3237 airports and their respective connections, the team created a web representing the global airline network, and found the primary strength of the system to rely on a triangular redundancy — when the route from airport A to B is unavailable, airport C is used.
The team then removed airports from the bottom up with only one connection, then two, then three, etc., leaving 73 of the most-robust airports including Chicago, Los Angeles, Heathrow, Dubai, Frankfurt, and more, each sporting almost 400 triangles. Even after removing these 73 airports, 90 percent of the grid is still connected.
Researchers also found, however, a group of periphery airports connected via star-like patterns that are highly vulnerable because they don’t connect with any triangle airports. Remove one of these, and an entire portion of the world covered by the corresponding star grid becomes completely inaccessible.
Take St. Petersburg airport in Tampa Bay, Florida, for example, which has 24 connections and 24 flights. Were St. Petersburg closed due to a natural disaster, terrorist incident, or any number of other scenarios, every one of its 24 connections is cut off from the global grid.
“It is surprising, insofar as there exists a highly resilient and strongly connected core consisting of a small fraction of airports together with an extremely fragile star-like periphery,” Verma and team said.
According to researchers such a network of vulnerabilities likely evolved from airlines’ continuing effort to minimize flight time while simultaneously maximizing profits.
“The scanty number of passengers traveling to and from remote regions only justifies the creation of a star-like network,” the team reported.
In order to better secure the network, airlines would have to ensure a direct connection between every pair of airports, which would also minimize flying time. The only problem is that such connections are only viable in regions of the world with bustling economies and dense populations, which many of the regions vulnerable to being cut off do not.