The Jet Mobile (ジェットモービル) is the first boss of Sonic & Knuckles, fought at the end of Mushroom Hill Zone Act 2.
To start the battle with the Jet Mobile, the player must jump on the weather-altering satellite dish to destroy it. This will restore the season back to normal and reveal Dr. Eggman/Eggrobo's heavily armoured Egg Mobile. If the player can hit his craft a few times before he moves offscreen, the battle will be easier to win. When Eggman/Eggrobo flies off to the right, the player should chase after him and follow him through an obstacle course comprising rows of spikes which the player must jump over/between to avoid (when playing as Knuckles the Echidna, there is an additional spike pattern that requires him to glide). If they keep running, they'll catch up with Eggman/Eggrobo. When he switches off the boosters, they can hit him. If the player has a Flame Shield, the boosters' flames won't hurt them, so they can attack Eggman/Eggrobo repeatedly without having to wait for the boosters to turn off. If they're fast enough, the player can also hit his craft directly from below, avoiding the risk of collision with the boosters thus allowing them to score a hit whether they are on or not.
After eight hits, Eggman/Eggrobo's machine starts to explode, but he doesn't look too worried. However, the Jet Mobile soon crashes into a tree and its armour falls off. After freeing the animals from the Egg Prison, the character will look up and see the Flying Battery Blimp fly past. Eggman/Eggrobo flies up in his now-basic Egg Mobile and enters the battleship, which the player then jumps and grabs onto, following him to the next Zone.