What would be the best way to "un-fix" a panel when you switch to landscape?

What would be the best way to "un-fix" a panel when you switch to landscape?

Using a fixed panel with a long-ish navigation list. However, when I switch to Landscape, the panel is still fixed, hiding some of the nav links. 

This is mainly a problem with Android native browsers. Chrome seems to recalculate the viewport vs panel height, and unfix things properly. But the native browser? Still fixed. 

Tried using media queries and switching to pos:absolute, but this seems to add more problems than it solves. 

Suggestions?