Originally Posted by Tom Pedale
The advantages of aluminum are its low costs with respect to strength to weight ratio. It is also relatively easy to form this material into different shapes and it is not difficult to weld. One disadvantage is that of all the frame materials used (steel, aluminum, titanium and carbon fiber) it will fatigue quicker (i.e. fail)due to the nature of the metal. I would consider this a factor if I were choosing a mountain bike frame that would be heavily thrashed for many years. For a road bike, it's a non-issue. If it were an issue, jets would be built of something else.
This is actually not true. The parts on airplanes are designed to fail due to weight requirements. It is just that the parts are replaced prior to their calculated failure point. Furthermore, rigid inspection requirements are put in place to look for hairline cracks...