How do aerospace units gain altitude in the abstract aerospace system? The Strategic Ops book, beginning at pg. 18, states that all aerospace units must move at least one zone per turn. It also specifies that units that have thrust rating of 10 or higher can use any movement left over to gain one altitude. What about the units that are slower than ten? If they MUST use their single movement to move to another zone, how do they gain altitude? This is important after, say, a strike at units on the ground map, where the striking unit must decrease one altitude to perform the strike... You obviously would want to gain your altitude back later on, but the book isn't clear on how to do that. Thanks!
