Flying Battery Zone

Flying Battery Zone is the second zone of Sonic & Knuckles. Acting as a flying vessel for badniks and capsules, Sonic and Knuckles infiltrate the airship on their pursuit to stop Dr. Eggman and the Egg Robo respectively.

Flying Battery Zone also reappears as the fourth zone of Sonic Mania. Its return is broadcasted after beating Studiopolis Zone, where Sonic wastes no time to get onto the ship as soon as possible.

Development
During the development of Sonic the Hedgehog 3, Flying Battery Zone was originally supposed to be apart of the first half of the adventure, between Carnival Night Zone and Ice Cap Zone. Developers have gone on record saying that the snowboard in Ice Cap Zone was originally going to be the door that gets kicked off at the end of Flying Battery Zone. Judging by the November 3rd 1993 prototype of Sonic the Hedgehog 3, the zone was likely split from the first half due to how incomplete it was near the release deadline.