In single-player mode, only flyable planes are flyable (obviously). In multiplayer, flyable planes and AI planes are flyable, under certain conditions (see my response to your other post on the topic). Flyable multi-engine planes are: He-111, TB-3, and Me-262 Non-flyable multi-engine planes are:
Me-110
B-17
C-47
Ju-52
DC-3
Pe-8
Pe-2
Pe-3
Su-2
Tu-2
Ju-88
Bristol Blenhiem
IL-4
Am I forgetting any, Hot Space?