Why is aluminum used for planes?

Answer: Strong but very lightweight

Cheapest metal to manufacture — Wrong. While aluminum is cheaper than some metals, it's chosen for aircraft because of its strength-to-weight ratio. Aluminum alloys provide good strength while being much lighter than steel or iron—critical for flight efficiency and fuel economy.

Aluminum never rusts or corrodes — Wrong. Aluminum does corrode, forming aluminum oxide (which fortunately protects deeper layers). Aluminum is used because it's strong yet lightweight—critical for aircraft. The strength-to-weight ratio allows planes to be structurally sound while minimizing weight for fuel efficiency.

Strong but very lightweight ✓ — Correct! Aircraft require high strength-to-weight ratio. Aluminum alloys (especially duralumin—aluminum with copper, magnesium, manganese) provide excellent strength while being about 1/3 the weight of steel. This reduces fuel consumption while maintaining structural integrity. Modern planes also use titanium (stronger, more expensive) and composites (even lighter), but aluminum alloys remain important.