How to play in Simluation mode?

[Parmenion]

Hi there.
Just got to say that I never liked aeroplane games before I bought this and now I'm hooked.
However, I can't seem to play in simulation mode. I checked through the manual and did a search of the forum but can't seem to find the answer I need.

I started the game in Arcade mode and have got to the Battle of Stalingrad, but I though that it was too easy and decided to start again but in Sim mode. The option to do so doesn't exist when I start the game though. Am I missing something simple?

Thanks in advance,
Parmenion