With the Hoverjets, make sure you familiarize yourself with the two abilities that gives you (holding Jump in midair to slowly descend, AND holding the Dash button after a grounded dash to continue dashing horizontally - this also works when you go off a ledge, allowing you to dash over large gaps).

With those two new movement abilities at your disposal, go back and explore the upper area of the Caves until you find another upgrade, then head to the upper areas of the Summit and explore there using that new upgrade.