In April of 2010, an Icelandic volcano erupted largely without warning. It left travelers throughout Europe stranded as tons of volcanic dust and ash spewed into the atmosphere and grounded planes. By the time the airports reopened five days later, 60% of European flights had been canceled, affecting more than 100,000 travelers.
While that was bad, the volcanic eruption could have been much worse. In the past, eruptions have occurred—such as in 1816, the so-called Year Without a Summer—that are so powerful that air-borne detritus resulted in year-long winters. If Europe was to have another Year Without a Summer, it could also mean a year of airports shutting down.
If that were to happen, how well could the world's air traffic network cope? To find out, Trivik Verma at ETH Zurich mapped the world airline network of 18,000 routes between 3,237 airports, tracing the myriad connections.
The network, it turns out, is pretty robust. The average number of connections between any two airports on Earth is four connections, with the largest distance between any two locations on the planet being 12 connections. There are about 73 airports like Frankfurt, Heathrow, Dubai, Chicago, Los Angeles and so on that connect more airports than anywhere else. While a volcanic eruption grounding flights at one of these major airports would suck for travelers, it wouldn't actually do much to disrupt the worldwide air traffic network.
It's the spots at the periphery of the world's air traffic network that are most vulnerable to disruption. For example, the St. Petersburg airport in Tampa Bay, Florida has 24 connections to airports that aren't otherwise served by the global network. If a volcano erupted outside of Orlando forcing St. Petersburg to close, these 24 peripheral airports would be entirely stranded.
So the next time a supervolcano erupts, the most populated parts of the planet will be inconvenienced, sure, but they'll be able to reroute traffic around them. It's the millions of people living on the edge of the worldwide flight network who really have to worry.