Tails: Toxic Skies is the first Challenge Act for Chemical Plant Act 1 in Sonic Generations, as well as the second and final Challenge Act that Tails appears in. As it is an Act 1 Challenge Act, only Classic Sonic is playable.
In this Challenge Act, Classic Sonic runs through Chemical Plant, but he is greeted by rows of spikes that are too long to jump over and long expanses of sky that he cannot cross alone. In these instances, marked by a circular blue sign with a yellow exclamation point, the player must press the Triangle/Y button to summon Classic Tails. Tails then appears directly above Sonic, who must jump to grab on to Tails' hands. In order to fly left or right, the player must move the Left Control Stick left or right. The player must repeated tap the X/A (jump) button to fly up, or refrain from pressing it to slowly descend. Once Sonic's feet touch the ground (or if the player presses the Circle/B button), he lets go of the fox's hands, and Tails disappears in a puff of smoke.
Halfway through the level, there is a vast gap that Sonic and Tails must cross to reach the goal. Sonic must fly across with Tails, avoiding balls of spikes and lasers in the way. There are also green rings that give Tails a short boost should be pass through them. Once Sonic passes the Goal Post, the mission is completed, and the player is ranked according to his/her score.