XSEED delves into the multiplayer of Sky Crawlers
“It supports a second player manning a secondary gun from the plane. Basically, the second player points the Wii Remote at the screen and fires while player 1 plays normally. This mode can be used anywhere in the game, though there are not levels made uniquely for this feature.”
There you go. I thought it would have been splitscreen multiplayer missions but I guess not. So it’s more like Yoda mode from the Call of Duty Wii games and the co-op in Super Mario Galaxy.