The Jetboard was first introduced in Jak 2: Renegade. It's ability to float may be caused by the same device that made the Zoomer from Jak and Daxter: The Precursor Legacy float. Anyways, Jak walked in Keira's Mechanic building because Krew told them to. Jak didn't know it was Keira. But they seemed to have a love interest in each other. Keira told Jak to go in the JET-Board Stadium and practice and if he was good, he could keep it, and be in the race. So first, you go on a training course where you are taugh all of the moves. Then, you are put in the Arena and play a thing where you have to earn a certain amount of points. So Jak wins and keeps the JET-board and it is needed in certain missions to cross Dark Eco. In Jak 3, Ashlin begs Jak to go back to Haven City and gives him the JET-Board. Jak can use it to ride, as a weapon, and to cross lava. It seams to change design from Jak 2 to Jak 3.
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