Duty Missions offer players a way to "grind" experience while being presented with a progressive challenge. Always take out the Y-Wings ASAP, because they DO shoot missiles. Eventually, a gunship will spawn, and those are really tough solo. Once you've gained enough starship XP, you qualify for Tier 2 missions (and better ships/parts....although it's hard to beat the 96k mass Heavy TIE Fighter shown here).