Originally Posted by davisew

Apparently you spend most of your time north and east of Charlotte.

This behavior has to do with how iOS caches its vector-based maps. Vector maps are more data efficient vs. the bitmap-based maps that other services use, therefore this cache can hold a fairly large geographic area.

Unless you pay for Gogo, you won't have a connection to Apple's Maps server, so the phone will show a grid where it doesn't have any data in its internal cache covering the area you're viewing.

If you were to open the Maps app while you have a data connection before departure and scroll around the expected flight path, then you'll load that data (and have that it in the offline cache) and will be able to follow the flight.