In the original H.A.W.X. you could fly any single player mission with any of your unlocked fighter jets and weapon loadouts. I've recently played through the H.A.W.X. 2 single player campaign (rather short, of course) and would now like to revisit some of these missions with different jets.
In the main menu, when you select "Single Mission" you're given the choice between "Story Settings" and "Custom Settings", but the latter is greyed out. Thus my question: How do I unlock the "Custom Settings" option for single missions?