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Like the rest of us, I am sitting watching as the West prepares to go to war against terrorism. It would seem as if, with the technology we have, we cannot lose, and yet that very symbol of our potency, the towers themselves, were fallible, and so I suspect is any military campaign.

What is remarkable is that we believed it wouldn't happen. Despite the international conferences where the police and security gathered to set out their doomsday scenarios, we didn't imagine the horrific consequences of the attack and, more to the point, didn't set up the systems to stop it.

While we were designing a "star wars" system against a rogue nation's missile attack, we hadn't put in place a system to protect our sensitive infrastructure and our towns and cities from hijacked planes being used as bombs.

What I imagine may have been suggested was the equivalent of a Star Wars forcefield over our towns and cities that would prevent planes entering. Most, if not all, planes are designed with automatic landing systems that can take over a plane and land it under remote control in fog. They also have autopilots working on satellite navigation. It must have been considered that aeroplanes' onboard computers could have been programmed to recognise no-fly zones, which if they approach, trigger the autopilot so they are steered away. It seems far-fetched, until one discovers, on reading this week's New Scientist, that such a system "that overrides the pilot" is used by fighter pilots as an "automatic ground collision avoidance system".

What is of more concern to engineers responsible for imagining doomsday scenarios is how fallible we were, too. We had designed the towers to take the impact of a plane, but had we ever designed for the fire that would follow? Had we ever sat down with aviation experts and developed the full scenario? Clearly, if we had, we didn't tell the fire authorities in New York. This is a major systems failure, for it is not, with hindsight, beyond our ability to debate these issues and fairly quickly draw conclusions.

It is remarkable we believed it wouldn’t happen

Engineering has moved on considerably since the towers were designed in 1965, and we now have the means of simulating impact and fire, which will no doubt be used to tell us much about what happened. It could have been predicted.

However, what if we had set out the scenario? How would a government have reacted? Firstly, any prediction would have been made discreetly for fear of alerting terrorists to a target, and secondly, given the international nature of flight, and the lack of success that the Americans have had with tightened security, the adoption of any "autopilot default" system would have been resisted. Perhaps this will now not be the case.

There is an interesting parallel. Satellite navigation systems for cars are becoming standard. These can be used to stop a vehicle from exceeding a speed limit, or entering a zone outside certain hours. If adopted, such systems would prevent tens of thousands of deaths every year. Once, on grounds of civil liberties, it would have been untenable. Now, perhaps not.