This mods allows you to use jetpack. For start using jetpack, just press TAB+J
To fly up press "SPRINT" button(RShift, as default), to fly forward press "FORWARD" button(W, Up arrow, as default)
To fly up and forward press the same buttons in the same time. To fly down press "JUMP" button(Space, as default)
To leave jetpack press "Exit vehicle" button(F, Enter, as default)

Video: