[throwanem]

True, but if it's been detected at this level of activity, why wouldn't it have been detected before now at a higher level of activity than this? There are privately operated and often networked sensors all over Europe.

[pvaldes]

Exact. This is the right question here.

Maybe we do not have sensors in the right places that could detect them.

I'll suggest to place some sensors in regular airlines and see what happens for example.