If I've learned anything from Alternate History fiction, it's that in 90% of all alternate universes are timelines where A.) Hitler won WWII; or B.) people fly zeppelins instead of planes. Today we'll explore the latter.
Note: This week's column contains plot details regarding io9's Book of the Month, Cherie Priest's Boneshaker.
If you're going to have everybody ride around in zeppelins, you'll need to explain why they're not flying planes instead. The simplest explanation is that planes don't exist, which is exactly what Michael Moorcock does in Warlord of the Skies, the first part of his Nomad of the Time Streams trilogy. The series is about an Edwardian man who keeps getting bounced around to new and different alternate universes. Warlord specifically deals with a world where WWI never occurs and the British empire never fell.
Unsurprisingly, Moorcock's book is considered a bit of a progenitor of Steampunk fiction, and a large number of zeppelin-heavy alternate history stories are extremely steampunk. Like Warlord of the Skies, S.M. Stirling's The Peshawar Lancers deals with a world where the British Empire lives on past its expiration date. In The Pershawar Lancers, a huge meteor shower in 1878 bombards the northern hemisphere and leaves England uninhabitable. After relocating to India and slowly recovering, the British Empire survives up to the novel's setting in 2025 with technological development largely halted at Victorian levels.
Some more recent examples of zeppelin-friendly alternate histories include Scott Westerfield's Leviathan, in which the titular Leviathan is a gigantic genetically-engineered war machine that can act as a zeppelin — it's not exactly a zeppelin, but it's so awesome that I'm giving it a pass. Cherie Priest's Boneshaker also utilizes airships. Zeppelins are the only way over the giant walls surrounding Seattle to hold in the (un)deadly zombifying gas that has destroyed the city.
In addition to the steampunk varieties of zeppelin, there are the pulp adventure-pastiche alternate universes. A great example of this is Airborn by Kenneth Oppel. Although the story is not specifically an alternate history, the characters live in a version of the 1930s in which airships are still used and large flying creatures live over the oceans.
Just because you have planes doesn't mean you can't have any fun. The setting of Crimson Skies is an alternate universe in which the US collapses under the weight of the Great Depression and air pirates rule the skies over North America in souped-up biplanes. The setting has become so popular that this board game-turned-multimedia franchise has now spawned two video games and several books.