In 1901, German metallurgist Alfred Wilm was working to harden aluminum-copper alloys. The work was not going well so in frustration he went on holiday (vacation). Upon his return, he found a harder material and after many years of work developed a commercially viable age-hardened aluminum alloy. Age-hardened aluminum, which is about three times lighter than iron, replaced iron in aircraft manufacturing. A photo of an early aluminum-bodied aircraft is shown below.
Age hardened aluminum is not as strong as iron so additional aluminum is needed which does offset some of the weight savings. The video in our later Synthesis, Fabrication, and Processing of Materials lesson has more on the use of aluminum in the construction of a modern commercial jet airliner. In the photo below is a Boeing 787 Dreamliner which utilizes a composite airframe, not aluminum. Boeing claims that this airliner is 20% more fuel-efficient than previous generations of airliners.
Now please proceed to the next section on one of my favorite alloys, a future star, a non-crystalline metal.