With the latest version of Map Pilot you can save basemaps while you have connection so you can use the saved mission in the field. You can also create new missions using that cached basemap. You cannot currently save a new mission that is created while viewing an already saved cached mission but that is on the way.
The standard Apple Maps caching is still a mystery to us and it is not to be trusted. Our caching will be there until you manually delete the saved mission.