Why are aluminum-copper alloys used in aircraft parts?

Aluminum-copper alloys are extensively used in the aerospace industry primarily because they can develop significantly higher strength than many other aluminum alloy groups.1

In aircraft construction, these alloys—often referred to as duralumin—are valued for their high strength-to-weight ratio, which makes them comparable to soft steel while remaining much lighter. Specific applications include:12

• Structural Components: Alloy 2024 is used extensively for the fuselages and lower wing sections of both civilian and military transport aircraft.1
• Specialized Performance: Magnesium-free variants like 2219 are utilized for space vehicle fuel and oxidizer tanks due to their ability to maintain high strength at both cryogenic and elevated temperatures.1
• Weight Efficiency: Newer aluminum-copper alloys incorporating lithium are increasingly specified for their lower density, further improving aircraft efficiency.1

Because alloying with copper can reduce natural corrosion resistance, these parts are often clad with a thin layer of pure aluminum (a process known as alclad) to protect the strong core material.12