The corrosion of aluminum is detrimental because aluminum is a lightweight and strong material, but aluminum oxide is brittle and easily broken. If an aluminum plane component oxidized, the strength of the material would be compromised and the component would need to be replaced quickly.
The corrosion of aluminum is detrimental because while aluminum is nontoxic, aluminum oxide can be toxic and hazardous to the environment. Aluminum naturally oxidizes to aluminum oxide, so this process is often reduced by cathodic protection or alloy formation.
The corrosion of aluminum is beneficial because aluminum forms a thin impermeable aluminum oxide layer. This oxide layer adheres strongly to the aluminum surface and when scratched, the freshly exposed aluminum oxidizes to protect the inner aluminum once again.
The corrosion of aluminum is beneficial because aluminum metal is very flammable while aluminum oxide is not. Aluminum metal quickly oxidizes in the presence of oxygen to become aluminum oxide, making a safer material.