The fastest (and easiest) way to get this achievement is to load up “The Package” mission and select “Rally Point Bravo” on Normal. Go ahead and walk to the base you’d normally defend but instead grab a jetpack. Then you’ll use it to get on top of the base’s roof. Sit around and wait until one of the banshees gets closest enough, then use your jetpack to get above it. Wait for the prompt to hijack, hit x and voila–there’s your achievement!