The Fallen Star Pack Add-on for Warhawk has 4 trophies - 3 silver and 1 gold.
While flying a jetpack, kill an enemy (who is also flying a jetpack) with any weapon other than the Rocket Launcher.
Kill an enemy who is flying a jetpack by hitting him with any vehicle or aircraft.
Snipe an enemy who is flying a jetpack.
Kill a distant enemy from on top of the salvage crane in Tau Crater.