Yhyjyk

Aluminum electrical wire got a bit of a bad reputation in household wiring due to reacting badly with terminals not properly rated for aluminum. Properly handled, it works fine, but it's so distrusted for small branch circuits that distributors won't even stock it.

Aluminum is a worse conductor than copper, by almost half. But that only considers it by volume (e.g. Wire diameter). By mass, the advantage swings back to aluminum. Nearly twice the ampacity for the same weight. Where would that matter? Aircraft.

Transport class aircraft are increasingly electrical, like the bleedless 787 where electrical does much of the heavy lifting.

Is aluminum wire actively used in aviation? Or is it "taboo" like it is with houses?

Cable is not just the metal wire. It's also insulation, installation, cable channels, extra space at tight bends where cable flexibility is insufficient, and maintenance of said cable. Aluminum corrodes in a lot of conditions and happens to be one of the most fatigue-susceptible metals.

For these reasons, most aircraft wiring is copper and silver-plated or nickel-plated copper. Such wiring is reliable even under imperfect conditions.

But there are cases where different considerations prevail. Sometimes it's just the need to have some minimum cable thickness, for mechanical and handling reasons. Other times it's very thick wire that is easy to install in a reliable way even with aluminum.

So there is some steel, copper-nickel plated aluminum, similarly plated steel, and pure aluminum wiring in aircraft. Until recently, the latter has been mostly avoided for reliability reasons. Currently there is enough confidence in quality management and maintenance that aluminum wiring is getting more use in attempts to save some weight. Such savings will always come at the cost of more stringent maintenance requirements.

Specific percentages vary widely, but generally non-copper wiring accounts for more than 10% and less than 50% of overall wire weight in a production aircraft.