WHAT IF: EMP attack?

For years people are warning for possible EMP attacks. For me this is a scenario that gives me a lot of thinking about possible fallout on Aviation in general and Military aviation in perticular.

I was told in NBC classes that an exoatmospheric nucleair explosion would kill any non EMP rugged equipment. So what if an nucleair capable country or group launches a missile into space and detonates a nucleair warhead.
That would even the playing field wouldn’t it? And that would be an act of war doesn’t it?

And other questions:
Are planes EMP Rugged? Are Fighters EMP rugged? is ATC rugged?
Are sattelites Rugged? I know some miltiary assets are rugged but I think a lot of things would be destroyed.

And a little bit off topic; what if an cyber attack can give (about) the same effect, knocking down ATC, disrupting, C4, on a more locally scale.. would that be an act of war? I wander what you think…..

And has enyone info about EMP bombs/missiles and how it would be deployed?
As an tactical or strategic weapon?