Meet the Active Denial System, coming to a neighborhood near you. If you'd like to see one ready for daily use, just walk on down to the World Bank in Washington, DC, where for the past eight years or so there has been at least one parked on the street at all times. It's a microwave weapon, not an EMP weapon, but it is a directed energy weapon, deployed in this case against us.
http://en.wikipedia.org/wiki/Active_Denial_SystemAs far as an EMP device ready to take down a plane, well, they've been around for nearly 60 years. One example is the Spielbergian "explosively pumped flux compression generator." Developed in part by none other than Andrei Sakharov.
http://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generatorAnd of course, if the rumor that a single AWACS can roast the power grid of a small town with its downward looking radar is true, then it rates as considerably more dangerous--or useful--than, say, a cell phone or a laptop, which the airlines consider unsafe for use on board a commercial aircraft taking off or landing. That may be one reason why the goon squad comes out in force here every time someone mentions that white plane that was seen following Flight 93 just before it crashed.
If you'd like to see an older, less sophisticated example of a potential assassination by EMP, you may be interested to learn about the crash of UA 553, in which twelve people connected with the Watergate scandal died.
http://en.wikipedia.org/wiki/United_Airlines_Flight_553The inimitable Sherman Skolnick, however, tells it a little differently:
http://www.apfn.org/skolnicksreport/shistory.html