The advantage of drones in this regard is that they let you threaten a much larger number of people with a small payload. Short of a nuke, there’s nothing you could put into a shipping container that would come close to threatening a meaningful fraction of a major city. This gives them a deterrent value that never existed for states with lots of ordinary munitions, and so could be worth the cost of acquisition.
For terrorists, acquiring and using such weapons might be more prohibitive than ramming into a crowd with a truck. But the fact that it would be possible at all would encourage people to exploit the vulnerability, especially since drone swarms carry considerable shock and awe value for terror (unlike destroying a water treatment facility).
Most natural gas distribution networks are vulnerable to overpressurization which might cause city-wide fires and hundreds of casualties, a few terrorists can organize that by physically capturing relevant infrastructure. But for that they need technical competences which they lack, as no contemporary violent non-state actors really reach the sophistication of Aum Shinrikyo.
Your plan, however, requires not only engineering skills but time and money and production facilities. It’s not impossible that another AS-like apocalyptic sect will emerge in the future but it seems unlikely. Hezbollah might have the means to develop capability in the near future (as Yair Halberstadt has rightfully noted below) and it may be a natural outgrowth of their current drone program but they won’t be able to keep the program secret from Israeli intelligence
The advantage of drones in this regard is that they let you threaten a much larger number of people with a small payload. Short of a nuke, there’s nothing you could put into a shipping container that would come close to threatening a meaningful fraction of a major city. This gives them a deterrent value that never existed for states with lots of ordinary munitions, and so could be worth the cost of acquisition.
For terrorists, acquiring and using such weapons might be more prohibitive than ramming into a crowd with a truck. But the fact that it would be possible at all would encourage people to exploit the vulnerability, especially since drone swarms carry considerable shock and awe value for terror (unlike destroying a water treatment facility).
Most natural gas distribution networks are vulnerable to overpressurization which might cause city-wide fires and hundreds of casualties, a few terrorists can organize that by physically capturing relevant infrastructure. But for that they need technical competences which they lack, as no contemporary violent non-state actors really reach the sophistication of Aum Shinrikyo.
Your plan, however, requires not only engineering skills but time and money and production facilities. It’s not impossible that another AS-like apocalyptic sect will emerge in the future but it seems unlikely. Hezbollah might have the means to develop capability in the near future (as Yair Halberstadt has rightfully noted below) and it may be a natural outgrowth of their current drone program but they won’t be able to keep the program secret from Israeli intelligence