The flight chart data is already backed up, is it not? One way to get to the issue is to ask these questions, I think: "is the data copied from another source?

The flight chart data is already backed up, is it not? One way to get to the issue is to ask these questions, I think: "is the data copied from another source?" and "is the data needed in offline use?" (where data is some amount of data larger than Apple can handle) N,N = Documents Y,N = Cache N,Y = Documents Y,Y = ??? What about that last case? It's even more annoying with map tiles than flight charts, if you've ever spent time backing up map tiles when you know they're already backed up on the main map tile server.