In classic A World at War, Russia may place one airbase each turn from 1939-1942, and may place two airbases each turn starting in Spring 1943.
Airbases may not be placed in minor countries in the movement phase of the first turn of activation, association or hex control, as full supply would not yet have been traced to the minor country's hexes. The Western Allies may not place airbases in Russian-controlled hexes, and vice versa.D. No more than one airbase counter may occupy a single hex.
Two examples of counterair attacks against enemy air bases which do not contain air units come to mind. The first is a counterair attack against an empty air base to deny the air base as a refuge to enemy air units withdrawing from another counterair attack (18.523). The second is a counterair attack against an enemy port containing a TF to determine whether the TF contains carriers carrying NAS (17.3123, 20.164A).18.522 After one round of counterair combat is resolved:
There are a number of examples of this general rule. For example, air units which carry out operations during their player turn (18.42) and naval air units flying combat air patrol which land on air bases rather than carriers (22.463B), are inverted until the end of their player turn, at which point they may be uninverted and used during the ensuing opposing player turn - provided they are not redeployed (28.81).C. NEW CONSTRUCTION: Air units may not be uninverted until after the redeployment phase of the player turn in which they are constructed. If redeployed to a new base during the redeployment phase, they remain inverted through the following opposing player turn (27.82A).