This mission teaches you to toggle between primary and secondary weapons during combat. As I nobly demonstrated once or twice, it does no good whatsoever to launch missiles at fighters who are facing you head on, because they're just going to shoot them down. Furthermore, it's nearly impossible to hit an A-Wing (or a TIE Interceptor) with missiles, because they can boost their engines and outrun them. So it's probably better to just close in on A-Wings, make some evasive maneuvers, and chip away at them with lasers.