In Harm's Way: Wild Blue uses the StarCluster 2.5 System, with some significant differences:

* Play Fighter, Strike, Slick, or Gunship pilots, or SpecOps, Infantry, Armored, or Brown Water Navy characters.
* Play characters with Army, Marine, Air Force, or Naval backgrounds from anywhere in the world.
* Troupe Play: Players play several characters, each type representing one aspect of the Mercenary Company, as well as Staff Characters to run your Company.
* Honor/Practicality Mechanic: Adds to your chance of success due to your reputation.
* Notice: You have to accumulate Notice - the approval of your superiors - to advance in rank. In order to get Notice, you have to burn with zeal and throw yourself headlong in harm's way.
* Competitive Play: There can be only one Leader. One hero. Is it going to be you, or the guy sitting next to you?
* Create your own Mercenary Company and shape it to do the things you want to do.
* Create Contracts for your Company, and negotiate for what you want and need.
* Dogfighting system adapted to modern jets from the IHW:Aces In Spades and IHW:Aces And Angels games.
* New Beyond Visual Range missile combat system.
* Surface combat system for Riverine/Littoral boats and ground vehicles adapted from the Dogfighting rules.
* Personality Traits give your character bonuses in various situations.
* Professional Edges give your character bonuses in other situations.
* Specialty Schools make your character ultra-skilled and competent at a young age.