Don't forget there is also a problem with the voltage conversion, 220/240 in Europe and 110 in the US. So you'd need step-down transformers for the westbound journey and step-up transformers for the eastbound. And those long cables are heavy. And they might get tangled up with other aircrafts' cables although I suppose if they painted them in fluorescent paint they could solve that problem. Except at night. No, there's a solution to that too, really powerful searchlights on the 'planes, but that would use more electricity ................ oh well .............
Apart from all that, great idea.