Why is aluminum widely used in aerospace applications?

Aluminum offers excellent properties for aerospace: Low density (2.7 g/cm3) - about 1/3 of steel, enabling lightweight structures; Good strength-to-weight ratio - especially in heat-treated alloys; Corrosion resistance - natural oxide layer provides protection; Ease of fabrication - can be machined, formed, and welded; Cost-effective - relatively low material cost compared to titanium or composites; Good fatigue properties - withstands cyclic loading; Well-characterized - decades of aerospace experience, extensive database. Aluminum alloys (2xxx, 7xxx series) form 70-80% of conventional aircraft structures. Limitations include lower strength than steel, temperature limits (~150-200C), and susceptibility to stress corrosion in certain tempers. Modern composites are replacing aluminum in some applications, but aluminum remains dominant for many structural applications.