Successfully complete the Aircraft Boneyard asset and the Jetpack will be available near the entrance to the save area. Alternately, successfully complete the airstrip mission Green Goo for the Truth to gain access to a Jetpack located next to the abandoned airstrip AC tower (the building where you save). When wearing the Jetpack, press A to accelerate. You can strafe with White or Black. To still in mid air in the Jetpack, hold White + Black. You will know if you are not moving if the exhaust pipes are circling. To take it off, press Y. To put it back on, just walk or run at it. You cannot save, enter or exit buildings, or shoot with the Jetpack on.