It would be awesome to have global flight. The only feasible solution I can see is streaming scenery data from a server via a download.
The developers can provide users with 2 streaming options.
Option 1 is to stream satellite imagery of the terrain and 3D structures at airports only.
This would be the quickest download and smallest memory wise. If most flight will be performed at high altitudes, this would certainly be sufficient.
Option 2 is to stream satellite imagery of the terrain and all 3D structures for an area (airports, cities and landmarks. Level of detail we have currently).
This would be the largest amount of data to stream and would provide the most detail. This would be best for folks flying at low altitudes, VFR flying and/or flying helicopters in a city environment.
Real world weather would also be an awesome addition.
Just some ideas. Keep up the great work!