Trust betrayed: lessons will be learned from the Germanwings crash / Getty

So long as humans are flying aircraft, it is impossible to erase all risk and protect families from the horror that some are now enduring

The average wage earner in Britain, France, Italy, Spain or Germany has the immense good fortune to be able to invest a very modest amount of disposable income to travel effortlessly to foreign lands. You and I can visit great cities, explore new land- and seascapes, meet people and share their cuisine and culture. And while having the time of our lives, we get a sense of the essential humanity that binds us all together

Had I written that last week, I would have expected a healthy round of heckling about the environmental damage that aviation wreaks for what some will see as superficial gains.

This week, as the families of the 150 people who died on the Germanwings plane face untold heartbreak that will resound through their lifetimes, such words might look like unforgiveably bad timing. But please bear with me.

The families who waved off their loved ones from Barcelona airport on Tuesday morning, and the parents who were waiting at Düsseldorf to welcome their children from flight 4U9525, were aware that a tiny risk accompanied them on their journey. Who hasn't bid someone "safe trip" or asked for a phone call or text to confirm of a safe arrival?

Until this week, most of us were prepared to tolerate the minuscule risk that a flight might crash. Those of us who study the subject know that many accidents are survivable, thanks to the safety systems that have been deployed since commercial aviation began almost a century ago. More importantly, the airlines' obsession with chipping away at all the factors that could contribute to an accident has resulted in safety standards that transcend any other industry.

The 24-year-old Airbus A320 that Germanwings had assigned to this flight had been cared for by Lufthansa engineers so attentively that it was as good as a brand-new aircraft.

The air-traffic controllers who cleared it for take off worship at the same altar of aviation safety – which allows them daily to choreograph the three-dimensional dance in the busiest skies in Europe.

And the crew had been meticulously trained to deliver their priceless cargo – students and business travellers, adventurers and lovers, infants and grandparents – to new horizons or safely home.

Human intervention

What no one could contemplate was that a pilot – at the very heart of that commitment of care – could carry out an act of mass murder of unimaginable cruelty.

On Thursday morning, the French prosecutor, Brice Robin, revealed to the world the horrific sequence of events during the final minutes of the flight. He explained how Andreas Lubitz had used his knowledge and training calmly to engineer a situation in which 149 innocent victims would die at his hand.

"He was breathing normally right up until the moment of impact," said the prosecutor.

As we struggled to assimilate the facts, our assumptions and certainties seemed to be overturned. A massacre had taken place in the safe skies of Europe, on a plane operated by one of the world's most respected airlines.

Pilot suicide is sadly not a new phenomenon in some parts of the world, and remains a possible explanation for the loss of MH370 last year. But somehow Tuesday's tragedy felt shockingly close to home. Those passengers and their loved ones had placed their trust in Germanwings, in its parent airline Lufthansa, and in the astonishingly good safety record of European aviation. An hour after ascending into sunny Mediterranean skies, their faith was fatally betrayed.

Risk assessment

Within six hours of the shocking revelations, airlines began to announce that their flight-deck procedures would change to try to prevent any repeat of the Germanwings disaster. As with US airlines, it will now become standard operating procedure never to allow a pilot to be alone on the flight deck; a member of cabin crew will remain in the cockpit whenever one pilot is outside.

The move is partly to mitigate a risk that had previously been barely considered, and partly to try to reassure anxious passengers that the same set of circumstances cannot occur. I hope it works on both counts.

About the worst decision that a family could make after Tuesday's tragedy is to decide to drive to Spain this summer rather than to fly. By doing so they will heighten the risks they face by about one-thousand fold.

I empathise with everyone who has witnessed the grief of the victims' relatives, and decides that the joys of travel do not merit the risk of being enveloped by tragedy. But in every aspect of our daily lives we constantly tussle with risk.

When you walk, cycle or drive, you have no way of knowing the training, skills and qualifications of other road users, nor the mechanical condition of their vehicles.

When you fly on one of the superbly professional European airlines that keep us all connected, you can be certain about all of those aspects.

You can never hope to delve deep into the mind of those in whom we place our trust and our lives: so long as humans are flying aircraft, it is impossible to erase all risk and protect families from the horror that some are now enduring. But trust is all we have.