Is there are way to "tab" between the charts you want in order to switch around quicker than via bookmarks?
I'm told that the real EFB's allow the user to tab up to 5 open charts at once along the bottom of the screen and thus you can very quickly flick between the charts.
Excellent suggestion.
Been thinking about this one and how to implement it and make it easy to use. How about a toolbar just below the navigation bar that keeps a list of the last 5 viewed charts in a "segmented control". (this is the type of control that, in the App Store app lets you select between Top Paid and Top Free on the top 25 page)
It would probably take up too much space on the iPhone, but on the iPad it would be fine.
I will also make it so that when you go into an airport you will view the last viewed chart/page for it, rather than displaying FAC by default.