A plane carrying European Union chief Ursula von der Leyen was forced to land in Bulgaria using paper maps after its GPS navigation systems were jammed.

Jamming has become an "invisible threat that risks devastating air travel" and leaves civil aircraft "one step away from disaster", said Christopher Jasper, The Telegraph's transport industry editor. But how worried should we be?

What is jamming?

Jamming disrupts GPS, the satellite navigation system that uses radio signals from satellites to calculate position. Jamming effectively overrides this by broadcasting high-intensity radio noise in the same frequency band as that used by the navigation satellites.

So it's a bit like a "person shouting loudly in your ear" who stops you "hearing what someone is saying on the other side of the

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