Why are airplanes made out of Aluminum?

Why are airplanes made out of Aluminum?

Strong strength to weight ratio.  While the same can be said of exotic metals like titanium, aluminum is much cheaper. If not for the discovery of aluminum we would not the air travel system that we have today. Early airliners were made of wood until a famous crash where a beloved sports figure and everyone on board were killed. Wood rot was found to be the cause. It drew attention to the problem of using wood for building airplanes. Overnight almost, wooden airplanes were phases out and metal clad airliners like the Ford Tri-motor came into use.  .  Steel or iron is too heavy and other than exotic metals like titanium or non-metal structures like modern day composites were not known at the time. Aluminum is the metal of choice because of it's strength and lightness. Aluminum is not easy to refine from ore but it is the most plentiful metal on Earth.