Question

why aluminium alloys used to make aircraft body

Answer 1

because aluminium has a very thin layer of its oxide on the surface which prevents air and water from getting to the metal and thus it resists corrosion
these two properties make aluminium very useful.
it is the same case for titanium

Answer 2

aluminum alloys such as Duralumin is light, tough and resistant to carosine and hence is used to make aircraft body

Explanation:

Hope it's useful