Anton now that you released the video showing off the arcade mode

[Anton Yudintsev]

Originally Posted by GabeFan

Hopefully you won't have to "unlock" SIM mode by finishing the game in arcade or realistic mode. I'm hoping that it will be available in the game straight away from the beginning...

You have to unlock Arcarde/Realistic/Sim mode by finishing special tutorial missions (rather short). Arcade tutorial is required, others are optional.
That is done, to prevent casual player from unintendently selecting of realistic/simulation mode.

After that, you will be able to play Campaign in mode of your choise.