[petre]

Lightning + aluminium wire is a problem. I suspect an electrical current will form in the wire even w/o lightning because of static electricity. Also the wire is a hazard if it breaks and falls down. It will probably cut everything in its path.

[namibj]

Yes, probably. Maybe you'd have to fly it at a place where you don't need to worry about lightning. But that seems rather restricting. Though, for high-bandwidth applications, it might then be necessary to fly local power, and have the whole system sit over the cloud layer, at about 50km.

Regarding the damage from it when falling down, you have to remember that each fiber weighs 50g/km, and the wire is also below 1kg/km, even for rather low heights. This should not be a problem, considering the ease of breaking an optical fiber optic at any remotely sharp edge. A small bird (the size your cat can catch) could probably snap it if he hit's it with some force.

[petre]

It will create a lightning discharge path regardless if you fly it over the cloud layer.

1 kg/km • 50 km • 9.8 m•s^-2 • 50 km = 24.5 MJ

10 MJ = kinetic energy of the armor-piercing round fired by the assault guns of the ISU-152 tank

I think that's just about enough energy to cut just about any living thing in half. Maybe it work if the cable was made of spider silk or Kevlar.