I'm finding that it's sometimes difficult to select all air units of the same type to assign them to a control group since they move around so much. When I draw a box around them with land units beneath them, I also get the land units in the group, which I do not want most of the time.
Supreme Commander had hotkeys to select all units of the same type (CTRL+A selected all air units, CTRL+L selected all land units... can't remember sea units but it was probably CTRL+S).
Would you consider implementing these functions within AoS?