If your device is wifi only, you'll need to cache your map to the device first using the wifi connection. Once done, when you're at your flying destination that has no wifi connection the map will be there for you.
Inadvertently, in the beginning I did this myself & was disappointed to find it not there. I also turned off the auto cleanup video cache option in the GoApp. Not sure why but turning off that option seemed to leave my map cached much longer. Hope that resolved your issue.