Chaos rating: 3/10

The internet has revolutionised the way we travel. But what happens when the computer says no? In the spring of May 2017, British Airways found out the hard way when a power outage hit two data centres, grounding 672 flights over three days.

The outage led to 75,000 passengers having their flights cancelled, with significant disruption at Heathrow and Gatwick. The eventual compensation bill was estimated at some £58 million, serving as a cautionary tale for the wider aviation industry.

The millennium bug

December 1999

Chaos rating: 1/10

Looking back from the comfort of 2024, it’s tempting to view the “millennium bug” with a nostalgic chuckle. But IT experts have a different take, pointing out that things would have been very different if not for the hundreds of billions spent on upgrading the world’s computer systems.

In any event, the airline industry didn’t escape totally unscathed. After years of terrifying speculation about the impact of Y2K, disruption became something of a self-fulfilling prophecy as carriers were forced to cancel their New Year’s flights with passengers too afraid to book.

9/11 terror attack

September 2001

Chaos rating: 8/10

Given the scale of what unfolded on that day, focusing on cancelled flights feels insignificant – at least on a human level. Yet the unprecedented impact of 9/11 on air travel speaks for itself: following the complete closure of US airspace, more than 40,000 flights were grounded in the space of 48 hours.

Civilian air traffic would eventually resume on September 13, focusing first on the thousands of stranded flights forced to land at temporary destinations. While security protocols were ramped up immediately, passenger numbers would take two years to recover, with a 6 per cent drop in Americans flying domestically in 2002.

Boeing planes grounded

January 2024