Pixar is great at doing "floorless" scenes, where the characters have no ground beneath them. This movie has lots of scenes of people and things flying, dangling and falling, all taking place hundreds of feet up in the sky. "Up" takes us into the sky the way "Finding Nemo" took us into the ocean. Both movies also have scenes where the characters are literally in the middle of nowhere, like when Mr. Fredericksen looks out the window and all he can see is sky and clouds, just like when Nemo and Dory are trying to get to Sydney and they find themselves in open, empty ocean.
When Muntz sends the dogs out in little dog-sized planes to fight Russell, didja get the inherent pun? It's a dogfight! Y'know, in any other movie, there would've been some character saying "Whoa... a dogfight!" But to Pixar's credit, they didn't do that. They let me figure it out on my own. :}
The short before the movie, "Partly Cloudy", is unusual in that it takes place in a similar setting to the main feature (in this case, the sky) in contrast to previous totally unrelated pairings of shorts and features: Presto/Wall-E, Lifted/Ratatouille, One Man Band/Cars, Boundin'/The Incredibles, etc.