IL-2 Sturmovik: Forgotten Battles is a STAND ALONE product
The Forgotten Battles consists of:

20 single-player missions
10 multiplayer missions
5 new maps

Dynamic campaigns that are working on all existing maps of IL-2 Sturmovik and IL-2 Sturmovik: Forgotten Battles

Forgotten Battles offers all the gameplay of IL-2 Sturmovik, plus many new additions. These include (but are not limited to):

30 new flyable aircraft
23 new AI-controlled aircraft
New AI ground objects and vehicles for each new map area, with new 3D building models
Ranking and award system for Finnish and Hungarian pilots
Selectable custom user-made skins in single play mode for players and all AI aircraft
All IL-2 Sturmovik: Forgotten Battles aircraft available in Quick Mission Builder, except seaplanes and gliders
Improved flight dynamics
More realistic AI scripting to create more realistic battles
New engine management relating to radiators, superchargers and fuel mixture control for different altitudes
Online track recorder and editor
A New system of single play track recording and editing
Search lights and barrage balloons (including intercommunication with AA artillery)
New ships including the Russian battleship Marat, Russian cruisers Aurora and Kirov and German cruiser Niobe (but not limited to)
Play up to 32 players online in dogfight and in cooperative modes (depending on your internet connection)
IL-2 Sturmovik and IL-2 Sturmovik: Forgotten Battles are not.....

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Minimum Requirements:
Pentium III 800/AMD Athlon 700 or better 256 MB of RAM ( 512 MB is recommended) Windows(r)98/ME/2000/XP