[lobocinza]

I don't think an EMP from a ground explosion would be significant. At least for a something 30k feet above it as I believe the pulse to be shaped horizontally and weak. To generate a significant EMP you have to detonate a nuke at high altitude as to cause a secondary EMP due to Earth magnetic field.

Even if a plane is hit by an EMP I believe the engines will keep working and the plane will have backup controls. Unless it's a Boeing of the newer generation where everything is electrical/digital. And even if everything stops working it will keep gliding unless at an odd angle/speed at the moment of the hit. That said loss of instruments and radio would be painful. Components getting damaged depends on the magnitude of the EMP and a weak pulse might cause only transitory malfunctions.

Note: my knowledge on this subject is superficial and I'm probably wrong.