Formations are very useful, especially for air units and mining sappers.
Press "Alt" and a formation hot key to initiate the formation.
Alt-Q = Wide Circle (Very useful for fast air units to scout the map and remove the fog of war revealing POC locations and enemy units.)
Alt-W = Tight Circle
Alt-E = Single Point (All units move towards that point. Air units can stack with this formation) Useful when using War Pigeons to carpet bomb.
Alt-A = Vertical line
Alt-S = Concentrated cluster (This is the standard formation, best for blocking pocs)
Alt-D = Diagonal line ( N. West to S. East) Useful for mining air and ground.
Alt-C = Diagonal line (N. East to S. West) Useful for mining air and ground.
Alt-X = X formation
Alt-Z = Horizontal line
You can make your own custom formation by placing your units in the position you
wish to remain as a formation. Next hit backspace to select all of your units and
then press Control and a letter key that you want to assign to that formation to.
The formation is stored as a hot key which you can later call back with Alt-<chosen letter>.