Jet packs are devices built to provide flight for a short time.
These devices are attched to the backplate of armor and is clamped into place so hard it is impossible to take it off without a special method. The device works by having two small but extremely powerful magic jet engines. Those engines are welded to a rocket. The rocket provides the thrust to get you off the ground. The jet engines the provide the lasting lift to keep you off the ground. To land the rocket engine cuts and the jet engines lower you to the ground.
The whole thing is control by the control panel on the users greave.