-->"I laugh at gravity all the time. Heh heh, gravity."

As our heroes approach the North Pole, they hear rumours of flying people - not from the past, but still living, over at the Northern Air Temple. However, upon arriving, they discover not air benders, but ordinary refugees who have used technology to fly and do other amazing things. All this invention comes at a cost, however, often destroying the original architecture of the temple, and Aang finds himself distressed to see his heritage being destroyed. As he tries to come to terms with how much things have changed, the Fire Nation continue to advance, seeking out the refugees' technology.

!!Tropes:
* ChekhovsGun: The war balloon.
* {{Foreshadowing}}: Take a good look at the plans the Mechanist is working on[[Recap/AvatarTheLastAirbenderTheDrill ...]] Also take note of the Fire Nation commander's interest in the balloon wreck.
* TheCoconutEffect: Invoked, Sokka and the Machinist put rotten eggs in the sealed natural gas room to produce the common sulfur smell, and warn for gas leaks.
* GadgeteerGenius[=/=]ReluctantMadScientist: The Mechanist
* GunshipRescue: How the ending battle is won.
* InspirationallyDisadvantaged: Averted with Teo, who might be an excellent pilot, but this is never suggested to be because he is paraplegic, nor does anyone seem to consider him in any way unusual. The only notice anyone takes of Teo's handicap is when Sokka is impressed by his "glider chair".
* InspiredBy: Sokka and The Mechanist's idea of adding the scent of rotten eggs to the gas to identify the source of the leak is similar to the real world process of [[TheCoconutEffect adding ethanethiol to otherwise odorless LPG to make it detectable for humans]]. In fact, many of the Mechanist's inventions are inspired by real life. People told time with grooved candles before clocks (albeit not ones with gunpowder spaced along the fuse); hot air balloons have similar vents to those proposed by Sokka.
* SteamPunk: This aspect of the show is really amped up in this episode.
* StuffBlowingUp: The mountain is full of methane pockets. One of them is right beneath the Fire Nation's forces. Guess what happens?
* SwallowedAFly: When Katara tries out a glider.
-->"How do I land this—Ackk! Bug! BUG! That was a BUG!"
* WhiteAndWhiteMorality: Aang versus the refugees. It's a morally complex situation where no one is really right or wrong.
* YankTheDogsChain: After hearing about flying people at the temple, Aang is naturally crushed to learn all their flying is done with mechanical assistance.