Can copper be used for fuel line?

I've seen copper used numerous times for fuel lines. The one problem copper has in an installation such as this is that it "work hardens" and becomes brittle over time due to vibration, at which time it can crack. Aluminum tubing would be a better choice and is just as easy to bend. If you need sources PM me and I'll link you to some. Aluminum is used exclusively in aircraft with excellent results.