Use mouse to look around.
Press and hold ‘Space’ to take off and fly up.
Press ‘W’ to fly forward. And drag ‘Mouse’ to change flight direction.
When you are over the hellipad - release ‘Space’ button to land on the ARK.
NOTE: The jet-pack is more useful for the long jumps than for long flights. But it is a very effective equipment for diversionary missions behind enemy lines.
Note, that Jet-pack causes increased energy consumption. Do not forget to restore the energy level before each jump.