The Jet Mobile (ジェットモービル,Jettomōbiru?) is a boss from Sonic & Knuckles, as well as its locked-on form, Sonic the Hedgehog 3 & Knuckles. It is fought in the second act of Mushroom Hill Zone after the satellite attached to the top of it is destroyed by the player, forcing the boss to surface from being hidden in the ground.
Dr. Robotnik will not attack by himself; the way of him "attacking" are the spiked ball hurdles which Sonic, Tails, or Knuckles must jump over or dodge.
Defeating the Jet Mobile is by means of jumping and running. Sonic, Tails (lock-on only), or Knuckles must avoid the spike traps and the flames that it releases. If the player stops running their character will slowly scroll over to the left. As usual, this boss is harder for Knuckles.
A glitch sometimes occurs during Knuckles' story, causing Robotnik to be the pilot of the machine instead of the EggRobo. When defeated, it is shown crashing into a large tree, with a hole at the bottom of the tree just large enough for Sonic, Tails, or Knuckles to run through.
Oddly, whenever the Jet Mobile is damaged, the spiked ball hurtles are are seen taking damage (meaning they also flash when the Jet Mobile is hit).