You could have an alternate history about Earth where certain major events did not happen such as the Wright Brother's successful flight at Kitty Hawk, and the Hindenberg disaster.
Perhaps Orville and Wilbur Wright gave up before they figured out how to design a working aircraft. Maybe Adolph Hitler died of syphilis before he could get into power, and Germany never entered WWII.
In a world such as that, it would be logical that the airship would still be widely used today.
As far as geography goes, a world without navigable many navigable waterways would make it impractical for ships to transport cargo and people. A lack of solid, flat ground would be a big problem. Airplanes are heavy, and require very solid ground to land on. If most of the land was swampy/marshy then there wouldn't be a good place to build runways. Large mountains would also pose issues. Travel by train would also be impractical in those situations.
