Andes are dry and cold and will preserve things. People hike the Andes. People can see things from above in the Andes.

The ocean is deep. Sediment drifting down from above layers the debris. Ocean currents disperse the light aluminum fragments that remain from the ocean impact.

An undersea landslide covers the fuselage or it slides down into an underwater canyon, separating and breaking apart.

I vote "forever".