"Goes on Air" is the fourth episode of season four and the forty-third episode overall of the animated children's series The Magic School Bus. It originally aired on October 4th, 1997.
"We got assigned air, and it's not fair!" The only contribution the kids in Ms. Frizzle's class have made to the Walkerville Space Capsule is an empty jar. "It's not empty," argues Keesha. "It's filled with air!" "But air doesn't do anything!" Ralphie argues back. They discover that's not so when the bus shrinks and gets stuck inside the jar, and they find that their only hope for escape is...air!
Keesha and Ralphie are arguing about the uses of air and Ralphie tells her that a jar is useless for the Space Capsule. But Keesha argues that an empty jar is filled with air. Ms. Frizzle's class meets Ms. River's class, who have built a project demonstrating the action of water. Ms. Frizzle's class regret not doing their project on water instead of air since water does something. Ms. River's class also has a project of a volcano to demonstrate the information of rocks. Just then, Ms. Frizzle arrives via bus and the class tells her that they are stuck on air. So Ms. Frizzle sends the class to the bus and Liz shrinks the bus inside the empty jar.
The class exit the bus and a woman closes the jar with a lid. The class re-enters the bus and Liz hits the jar vacator, only for it to break down. So Ms. Frizzle reads the escape manual and exits the bus to open compartment seven for the escape kit. She opens the kit and the pink clouds, named "extraordin-air" colored in pink to see, permeates the jar. Ms. Frizzle also reads that the extraordin-air to escape through the top of the jar. Unfortunately for the class, the Space Capsule is set to launch in exactly ten minutes.
So the class finds out on their own what the extraordin-air can do. Ralphie catches some with his baseball cap, but it ends up escaping out. Dorothy Ann reads in the manual that the extraordin-air disperses in multiple directions. Liz discovers a way to catch the extraordin-ar using a turkey baster. But Ralphie states that it would take more than a turkey baster to catch all of it. So Ms. Frizzle searches in the escape kit and pulls out an elastic rubber glove. The class uses the glove to catch most of the extraordin-air and attempts to seal it to keep it trapped. D.A. reluctantly lets the class use her hairbands to seal the glove to keep the extraordin-air from escaping out. The class then learns how the extraordin-air pushes anyone on top up once someone else pushes down on the glove and that the extraordin-air can be pushed in any direction, as well as changing colors once it is squeezed in a smaller space. Arnold also compares the extraordin-air to a spring pushing back a person trying to push it down. So Keesha decides to push all of the extraordin-air into the larger part of the glove to make it springier to bounce someone to the top of the jar. She volunteers to do the job and the class rolls up the fingers. Wanda and Phoebe jump onto the glove, sending Keesha flying to the top. Unfortunately, Keesha doesn't get high enough and begins to drop right back onto the glove. So the class squeeze in the rest of the air inside the glove using Ms. Frizzle's air pump, growing the size of the glove. Suddenly, the glove pops and the top flies out of the jar. Keesha, who was on top of the jar, begins to fall down.
She lands onto a net provided for her by the bus. The class then learns that the Space Capsule is about to launch in three minutes. Wanda discovers a cork pump in the space kit and Arnold inadvertently gets the idea to use it to pump the class out of the jar. The class decides to make a giant cork popper along with a big, strong air tank, using it to squeeze the extraordin-air inside to build pressure and release it through the cork popper to use the pressure to blast the students out. The only problem is that all of the extraordin-air got depleted. So Keesha suggests that the class should use ordinary air to escape out of the jar. As the Space Capsule is now ready to launch, Keesha decides to use a lot of air pressure to blast her high to catch up to the Space Capsule to put something inside while in the air. The class decides to use the cork popper. But Keesha wants to use more. So the bus transforms to a giant cork popper and provides a tank big enough to hold a prolific amount of air inside, as well as three high-pressure pumps and one pod for two. Keesha and Ralphie enter the pod and the rest of the class pumps the air. Liz releases the pressure valve and the pod Keesha and Ralphie are inside blasts out just in time to catch up to the launched Space Capsule. Keesha decides to go with Carlos' idea of a poem ("Air is here, air is there, down on earth, it's everywhere, what it does is hard to tell, 'cause air does invisible very well, pushed air is all snugged and tight, it pushes out with all its might, but best of all, if you need a ride, air under pressure can provide") and the pod catches up to the Space Capsule, using suction cups to adhere to it. Ralphie stores the cork popper and the poem inside and returns to the pod, which lands safely down the ground below. As Ralphie and Keesha meet the rest of the class, Ms. Frizzle states, "Just like air, my class works best under pressure".
- In Ms. Frizzle's escape kit, a pair of boxer shorts are seen, much to the disgust of her class why such an item would appear in such a kit. This is the only episode to mention any humor regarding underwear.