HOW THE GAMEPLAY INTERSECTS WITH GAME STORY LINE?
In single player mode of Skyjacker we play different missions, progressing in ranks, while the global story line progress on the background is changing gaming environment. Here is a rank chart You can juxtapose it with story line too.
Player has a freedom of choice inside of each mission, but there is a global story line of the Galaxy, and missions types submit to the global storyline. I.e. you cannot play any military mission before the Global Galaxy War begins. Same way, you cannot get any mission against Shaarkarians before their invasion happens.