Here are some numbers around what the main combatants look like. For information on the Axis Allies the 8MP Axis thread goes into detail on what is available there.
The Luftwaffe begins the 1941 campaign with approximately 3,200 aircraft in the field and another 800 in reserve. By aircraft type they break down to these rough numbers:
Recon- 670 deployed, 220 in reserve
Level bombers- 990 deployed, 420 in reserve
Fighters- 800 deployed, 210 in reserve
Fighter bombers- 160 deployed, nine in reserve
Tactical bombers- 340 deployed, none in reserve
Transports- 385 deployed, none in reserve
The Soviet air forces total approximately 12,500 aircraft at the start. Broken down by type, they break down roughly as follows:
Fighters and fighter-bombers: 150 regiments and 31 battalions containing 7,000 aircraft
Tactical/Dive Bombers: 20 regiments and 3 battalions of 800 aircraft
Level bombers: 104 regiments and 14 battalions of 4,200 aircraft
Recon and Strategic Recon: 12 regiments and 1 battalion of 400 aircraft
Transports: 5 regiments of 60 aircraft
In most cases, the Axis turn 1 will result in the loss of between 4,000 to 6,000 Soviet aircraft. Soviet air regiments are 40 aircraft on turn 1 but are halved on turn 3 to 20. As a result, a lot of aircraft will be filling the reserve pools of aircraft. This will be offset slightly as battalions over time can upgrade to regiments. Prior to turn 8 in the 1941 campaign scenarios, no new air units may be built. Starting on tun 8, up to 8 air units can be created in addition to one airbase.
Organization and Airbases- The VVS initially operates on 80 airbases under 20 different air commands. Some of these are associated with ground fronts while others are not. As an example, the Long Range Air Command operates 4 BAK (air corps) until turn 10 at which time they are automatically disbanded and two air commands are dedicated air defense HQs dedicated to the protection of Leningrad and Moscow. There are two naval air commands: Baltic Fleet and Black Sea Fleet which are there primarily for historical purposes as there is little in terms of naval operations in the game. A total of 28 airbases are SADs and all of these will be disbanded at a rate of three per week beginning on turn 34. That is the first week of February 1942. Normally I start building new airbases early on at a rate of 1 per week in order to offset the loss of the SADs. There are some airbases that support the two naval commands, designated by the abbreviation KBF. Typically I disband these when I have the opportunity and replace them with other types of bases. That said, there is no reason why people can’t keep and use them for any purpose desired.
Leadership- Each air command at the start of the game is led by a general with an air rating from 3 to 6. The Soviets do not have a wealth of good air leaders during the Summer of 41. Generally I am looking for air leaders with an air rating of 6 and an admin rating of 5 or more. A good admin rating will result in more damaged aircraft being repaired and not lost. During the first 15 turns, these leaders include A. Novikov who already commands Northern Air Command, N Skripko and V Sudets who command 3rd and 4th BAK respectively, F Falaleev and T Khryukin who start in the reserve pool.
Anti-Aircraft Artillery or AAA
This version of the game initially contains 231 PVO AA regiments and battalions as support units. Some of these are lost as cities are surrounded. Locations such as Lvov and Bialystok will lose them on the first turn if the Axis pockets cannot be opened. However, with nearly 9,500 guns among the units in cities and on map HQs at the start, a fair number can be put into service to support the Soviet effort. There are admin point costs associated with removing these SUs from cities.
15+ hexes = 50AP
<15 hexes = 25AP
<10 hexes = 13AP
< 5 hexes = 1AP
15+ hexes = 15AP
<15 hexes = 8AP
<10 hexes = 4AP
< 5 hexes = 1AP
Since a battalion in this case is only 1/5 the size of a regiment, it doesn't make a lot of sense to pay costs of more than 1AP for the battalions. In other words, leaving battalions where they are is a good idea until the enemy gets from 1-4 hexes distant. Regiments pretty much the same. You could conceivably do it when the enemy is 5-9 distant, but the cost is pretty high. Anything over 10 hexes and you're really wasting AP.