From a Controller point of view, I had many moons ago the "chance" the have an African registered DC8 on the frequency that did experiment a total electrical failure ( pre-RAT days) and requesting assistance , the old trained phraseology came handy : : start turn left now , stop turn now. " calculate distance vs altitude and say "start descent now 500ft/min" , etc.., the guys were completely lost over a foreign country (for them) in IMC. A GPS would have come handy but we got them down safely after finding a VMC open suitable airport below (was not that easy ), and all this using an old 6 RPM long range primary radar ( update every 10 seconds.) of course with no mode C altitude reporting.
I wonder how many controllers and pilots are trained today on this.