Jetpack can allow you to fly in the air but it requires a battery. After flying for some time, you need to recharge the battery to continue.
How to find it?Edit
In story mode you can find jetpack in Chapter Five after you get to the Desert City. Ava in the Abandoned Desert City will be selling one.
After the 0.9a update the jetpack is given to you by Hitomi during the quest to look for crystals, before the Desert City
How to use it?Edit
The Jetpack requires a battery in your equipment inventory. The Jetpack can be used by pressing and holding space to ascend. Steering is accomplished with the movement keys. The Jetpack must be placed in an equipment slot to be used.