Why is aluminium widely used in aircraft construction?

The correct option is Corrosion resistance and light weight.

Aluminium is extensively used in the aerospace and aircraft construction industry due to a combination of key physical and chemical properties:

1. Light Weight (Low Density): Aluminium has a very low density compared to other structural metals like steel. This high strength-to-weight ratio allows aircraft to be significantly lighter, which improves fuel efficiency, increases payload capacity, and lowers operating costs.

2. Corrosion Resistance: Aluminium naturally forms a thin, protective oxide layer (${\mathrm{Al}}_2{O}_3$) on its surface when exposed to air. This prevents further oxidation and corrosion, making it suitable for withstanding harsh atmospheric conditions at high altitudes.

Therefore, its combination of corrosion resistance and light weight makes aluminium the ideal material for building aircraft structures.