It was clear that something had gone seriously wrong with the thousand-strong swarm of drones twinkling above Darling Harbour during the Vivid Sydney festival last month. Many suddenly started flying out of formation. Almost 90 fell from the sky and into the dark water below.

Thankfully no one was injured. Yet the drone show failure, which has been blamed on radio interference, highlighted a challenge facing all autonomous aircraft: what happens when things go wrong?

This is an important question, given autonomous air taxis that fly passengers above traffic and autonomous drones that deliver packages across cities could become a familiar sight within the next decade. In the United States, for example, drone delivery company Wing recently announced it is expanding its partnership with Walmart across seven more cities.

These technologies will occasionally experience failures. But an aircraft cannot simply pull over to the side of the road. So safety depends not only on preventing failures but on ensuring aircraft can respond safely when they occur.

Designed to tolerate some failures

Modern autonomous aircraft have a range of features to ensure that no single failure leads to the loss of the aircraft. These include multiple motors, distributed propulsion, backup flight computers and software that can tolerate faults.

But even........

© The Conversation