Sorry, this one has been worked on for a while. New errata:
Changing Altitude (pg. 84)
After: "If a unit descends more than two altitudes in a single turn, it must make a Control Roll, with a modifier equal to the number of altitudes descended."
Add: "A unit attempting an air-to-ground attack this turn must declare it, and any corresponding altitude changes and skill rolls required, during the movement phase."
Air-to-ground Attacks (pg. 242)
After: "Aerospace units can only make one air-to-ground attack per turn, and cannot make any air-to-air attacks in the same turn."
Add: "Air-to-ground attacks must be declared during the movement phase, including any change in altitude and skill rolls that occur as a result."
Does that clear things up?