If your characters have entered a parallel universe that's just a few steps removed from our own, the fastest way to establish it is by sticking a whopping great Zeppelin airship in the sky.
In our world Zeppelins and other airships lost popularity in the late 1930s in part due to a series of catastrophic crashes (culminating in the the fiery Hindenburg disaster). These crashes were mostly caused by extremely primitive technology and the use of explosive Hydrogen gas for lift, but their eventual obsolescence in most fields except advertising and military observation was mostly due to advances in other aircraft technologies. More recently, airships are making a comeback for niches such as pleasure cruising, humanitarian aid, replacing helicopter for cargo hauling, law enforcement, military surveillance, photography, and scientific research. This resurgence has been enabled by new technologies and designs that mitigate the airships' disadvantages and greatly enhance their lift, safety and speed- by hybridizing them with airplanes and tiltrotors.
It is important to note that the presence of airships doesn't imply that the technology of the Alternate Universe is inferior. Just like with biological evolution, Zeppelins are not "more" or "less" evolved technology, what's used is whatever is the best available fit for the niche. It could just as well be that Zeppelins in the Alternate History were better able to suit the situation than airplanes were, say if there was a massive resource shortage that demanded efficiency and payload over speed, or some other economic factor.
Zeppelins aren't just the fastest way to indicate that you've found yourself in an Alternate Universe setting, they're quite often a striking symbol of dystopia. Like Spy Satellites, Zeppelins can be used to survey the populace, only hundreds of times cheaper and more effectively, with next to unlimited endurancenote Provided they do not encounter a storm, which would deprive them of solar power or cause them to use up fuel reserves to keep up with the winds. They are also much more visible than a satellite, obviously, often leading to their use as a Propaganda Machine, acting like Big Brother's evil Goodyear Blimp.
The name of Zeppelin strictly refers only to airships with a rigid external frame, a propulsion and steering mechanism, and no anxiety that users will be put off by the name. Alternate universe plane-spotters, take note.
So by filling up Earth 2 with bulbous aircraft rather than hovercars or spaceships, you are suggesting a world that is of a similar time period to our own, but just happened to follow a different technological route. It also helps that they have lots of Diesel Punk and Steam Punk cred and are sufficiently olde-worlde to be used in fantasy stories too. They are also cool.
Alternatively, the Zeppelins are just there to show the audience that the movie is set in another world, even if nobody from our world crosses over into it.
Alternatively, you could make the whole sky different. This works, too.
The transportation of choice for Sky Pirates everywhere. Also see Airborne Aircraft Carrier, Cool Airship, and Floating Continent. Somewhat related to Space Whale.
Kiki's Delivery Service has a huge polar exploration zeppelin as befits its Retro Universe setting. It also escapes its mooring and crashes spectacularly, proving that Kiki's world, while different, is not all that different from ours.
Things that look like airships roam the sky in Puella Magi Madoka Magica The Movie: Rebellion over Mitakihara. This is one of the first indications that something strange is going on. When the truth is revealed, the ships actually catch on fire and crash.
One of the more obvious differences in the Watchmen universe (which departed from our own when a genuine superpowered being came into existence in the aftermath of WW2 and singlehandedly won the Vietnam War for America) is the huge zeppelins that hang in the air over New York. note Zeppelins are more viable because Doctor Manhattan can synthesize helium in large enough volumes to make airships safe and cheap. Basing a whole industry on one individual — What Could Possibly Go Wrong??
The Invisibles by Grant Morrison has some of these early on when Dane and Old Tom trip their way to another London.
In Christian Gossett's The Red Star, the military power of the Soviet-esque Reds is based on their great fleet of "skyfurnaces," which are essentially kilometer-long flying battleships/carriers/troop transports that run on magic.
One of the few fantastic things to be found in any of the Marvel Noir stories is the O*N*E Dirigicarrier seen in X-Men Noir: Mark of Cain. And boy is it ever fantastic: it's a colossal battleship kept airborne by virtue of having several Hindenburg-like zeppelins strapped to its underside.
Thorgal has Mayincatec zeppelins. However, it's thanks to the fact that their Physical God ( actually a descendant of the spaceborne humans who left Atlantis) is capable of creating the gas to float them.
"Zeps" are the travel mode of choice in the 2031 setting of American Flagg.
Plan 7 of 9 from Outer Space by Odon. In the zeerust future of 2009, Captain Proton uses a vacuum-dirigible to travel across Mysterious Antarctica — vacuum which being literally lighter-than-air gives it lift, and propulsion is via corkscrew driving planes encircling the dirigible.
The 1997 film adaptation of The Borrowers has numerous indicators that is set in a mid-Atlantic Retro Universe, not least of all being the constant presence of one or more zeppelins in the sky.
Sky Captain and the World of Tomorrow (2004), set in a Dieselpunk version of 1939, opens with the Hindenburg III docking with the Empire State Building. While the building was in fact designed with a mooring mast the idea was dropped after tests with a U.S. Navy airship showed that wind turbulence caused by the surrounding skyscrapers made it too hazardous. Well, that and the fact that most passengers found the idea of crossing a gangplank 1000 feet above the street more than a little intimidating.
The film adaptation of The Golden Compass features airships in the establishing shots of the alternative Oxford.
In Stardust Robert DeNiro plays the captain of the airship Caspartine.
Despite being set in 2019, the Los Angeles of Blade Runner appears to be infested with zeppelins, most of which wind their way through the labyrinthine skyscrapers advertising travel to the Off-World Colonies and various Chinese/Japanese products.
One of the big differences between real 2009 and parallel universe 2009 in Southland Tales is the presence of massive perpetual-motion powered Zeppelins.
The Robert A. Heinlein book Job: A Comedy of Justice has the main character from a zeppelin-filled world, slipping into a world with no air traffic at all, and then into one with similar technology to our own. One especially well-done part is when he attempts to explain to the readers what an airplane looks like from the perspective of someone who's never seen one before. It's explained that in this alternate reality, heavier-than-air flight is proven to be mathematically impossible and The zeppelins travel at mach speeds!
Jasper Fforde's Thursday Next series features a world with zeppelins but no jet planes — although small propeller aircraft do exist. Of course, there's little demand for high speed airliners with the gravtubes: London to Osaka in 42 minutes! At one point Thursday has the option of being hidden in a parallel Earth where there are jetliners — presumably, from the sound of things, our world. She says such a thing as a jetliner is impossible.
The opening story in Elizabeth Bear's New Amsterdam is a murder mystery set on a zeppelin. With vampires.
The parallel world that takes up the majority of the His Dark Materials series features giant zeppelins as a mode of transport. Interestingly, they are handled much more realistically in the books than in the movie.
This is the premise of Kenneth Oppel's Airborn trilogy: an alternate world where, due to the existence of an ultra-light gas called hydrium, airships became the primary means of long-distance travel. Features lots of nautical metaphors. There's still an Eiffel Tower, but it's used for mooring.
Aaron Allston's novel Doc Sidhe is set on an alternate world where zeppelins and autogyros are still cutting edge aviation technology, and the climactic showdown takes place on board the major villain's airship.
Fritz Leiber's short story "Catch That Zeppelin!" is about an alternate universe where things turned out (mostly) much better than our own, It too includes zeppelins docking at the Empire State building, where a Real Life mooring mast was considered. Needless to say, they didn't use hydrogen to lift them.
Harry Turtledove's novel The Two Georges is about an alternate world where the United States never left the British Empire. The first chapter is set on an airship, where the protagonist sees a Air Force biplane fly past and echoes the general view that while such speed is useful for the military, there's just no need for it in civilian life.
This is in fact based on the Imperial Airship Scheme, also known as the Burney Scheme, which proposed that Britain's colonies would be serviced by a fleet of airships.
Mortal Engines has a lot of Zeppelins, though it's a post-apocalyptic future version of this world rather than a parallel one. Heavier-than-air flight is reinvented over the course of the series.
The War in the Air by H. G. Wells is about the German Empire using giant zeppelins to attack the rest of the world, particularly the United States. While at the time it was written, it was a reasonable extrapolation of the current technology, it suffers from being set Twenty Minutes into the Future and so might now be considered an honorary alternate reality.
During World War I the Germans did bomb London several times with zeppelins. They did a better job of frightening the civilians than actually destroying strategic targets, but it worked out all the same until they started getting blown out of the sky.
Dean Ing's The Big Lifters has a messianic protagonist pushing high-tech "delta-dirigibles" as a way to get big trucks (like the one that killed his grandmother) off of America's freeways.
The War Against the Chtorr. Blimps are used for military and rescue operations, but nothing beats the Hieronymus Bosch, a giant luxury airship (30% longer than the Hindenburg) converted for the scientific expedition in "A Season for Slaughter".
In Charles Stross's The Merchant Princes Series, one of the two alternate universes featured in detail uses zeppelins for air travel. (The other one has a roughly medieval level of technology, so it doesn't have air travel at all.)
L. Neil Smith's alternate history novel The Probability Broach features large zeppelin passenger liners. Interestingly, Smith does not have them simply for style, rather their existence proceeds logically from the nature of his world. The character's claim that zeppelin travel is uncommon in our world because the military subsidizes airplanes so that it can requisition them in emergencies. It does not subsidize the less militarily useful zeppelins, which means the incentives are for companies to develop planes. In The Probability Broach the governments and militaries of the world are much weaker, so are unable to subsidize much of anything. In fact, in the back story a sort of airborne militia try to use zeppelins in combat and are pretty much all shot down, lampshading the uselessness of these aircraft as air superiority fighters.
This turns up with the second word of The Haunting of Alaizabel Cray, a somewhat Lovecraftian novel set in an alternate late-Victorian London. For the record, the first word is "The". In our universe, when Queen Victoria died, Count von Zeppelin hadn't sold even one of his machines, but he had been banging on about them since 1874.
The Red Mars Trilogy has a fleet of automated "air"ships used both for exploration and as part of the early Terraforming effort (ultimately a failure but it turns out somewhat useful anyway), so they're Zeppelins on another world as well. Later (post-terraforming) a transforming high-tech sailboat turns into a blimp to escape rough seas.
Neil Stephenson's The Diamond Age features a very well justified abundance of airships. With ubiquitous nano-tech it's so simple to create objects that are lighter than air but stronger than steel that it's the law you have to add weight to things to make sure the atmosphere isn't filled with lighter-than-air-stronger-than-steel grocery bags clogging engines. As to the airships, when you can create these materials you don't have to fill the envelope with anything at all. Vacuum is lighter than everything and thanks to nanopumps cheap to create. Airships are so economical they replace shipping as the bulk transit of choice.
Iain M. Banks's Transition invokes this — a man who frequently travels between universes at one point looks up at the sky when arriving in a new one, searching for zeppelins. As he says, he 'likes it when there's zeppelins'.
In Michael Moorcock's Warlord of the Air, the alternate-timeline Earth is still using zeppelins in 1974, and has never developed heavier-than-air flight technology. The title character whose people have just invented heavier-than-air vehicles, claims that the imperialism of the Great Powers has stifled innovation.
The Hubris in More Information Than You Require, a massive zeppelin that the author buys from Emo Philips. Counts as another world because according to this book, Thomas Jefferson was friends with the mole men, axolotls have magical powers, and Enrico Fermi was an alien.
In the 1632 series, Marlon Pridmore uses his experience as a balloonist to help the Danes build a dirigible to bring home nutmeg from their Indian colony of Tranquebar. Also, without any experience, but with a lot of brute force, Berni Zeppi helps the Russians build their own dirigible, which they use to beat a Polish-Lithuanian army.
Of course, as antiques, those exist in our world, aswell◊.
Chabon may have been using the reference as an inside joke, since an Alternate History story always needs a Zeppelin.
The Windup Girl by Paolo Bacigalupi. Dirigibles powered by kink-springs and other alternate energies are used for international trade, as there's no petroleum any more.
Rudyard Kipling's short story "With the Night Mail" imagines a world where airships are the primary means of transatlantic flight - though when he wrote it, this looked like a probable future rather than an imaginary world.
The "blimps" that ply the "skies" of the giant living space habitat Gaia in John Varley's Titan trilogy are literally Zeppelins from another world. They aren't machines though: they are living, sentient creatures kept aloft by naturally produced hydrogen. Sometimes they allow people to hitch rides.
They're terrified of fire, for good reason. At least partially because of this, they (and most of the main characters) hate "buzzbombs", heavier than air flying creatures that have what amounts to an organic ramjet embedded in their bodies and are described as being something like sharks mentally.
The titular Leviathan in the Leviathan series is a living airship in an alternate history with organic technology.
In Tom Kratman's Caliphate, given the relative scarcity of oil but plentiful energy thanks to nuclear power, hybrid lifting body airships powered by pebble bed nuclear reactors are the most common mass transportation for both civilian and military purposes in many countries.
A variation in Taylor Anderson's Destroyermen. While the story mostly takes place on an alternate Earth, the airships in question were, in fact, invented by the Japanese for the Grik, most of whom are too dumb to operate a heavier-than-air craft. They are also shot down incredibly easy with by three P-40s with tracer rounds.
Stephen Baxter's Literature/Proxima ends with a band of explorers emerging on a world to be confronted by an airship piloted by an angry Roman.
Live Action TV
In the Doctor Who episode "Rise of the Cybermen", The Doctor immediately notices that they've slipped into a parallel world when he sees zeppelins in the sky above London.
The season six finale "The Wedding of River Song" opens with a montage of anachronisms ("Do Not Feed The Pterodactyls" sign, Holy Roman Emperor Winston Churchill, Charles Dickens interviewed on television, etc.) starting, of course, with a sky full of hot-air balloons. Carrying cars.
It's a relatively minor instance, but in the Stargate SG-1 episode "Past and Present," SG-1 finds itself on a post-industrial world remarkably similar to our own in the late 19th century. A zoomed-out shot of the city shows a zeppelin floating lazily in the sky.
There is an airship in the opening sequence of Caprica, and in the Metaverse game New Cap City, a gigantic, heavily armed dirigible circles the virtual city, launching fighter planes and gunning down anyone it sees on the ground.
The National Geographic Channel's Aftermath: Life Without Oil special suggests that a civilization without access to abundant fossil fuel may use airships for air travel; most likely thanks to the fact that they need very little fuel compared to propeller or jet-powered planes.
Played dead straight to the point of an Invoked Trope on Fringe; the first image Walter shows his military bosses in 1985 to prove he's discovered an Alternate Universe is a zeppelin docking at the Empire State Building. They're not seen all the time in other episodes set in the alternate universe, but then again you don't always see airplanes in the real world's sky. Sometimes, the transition from scenes in one universe to another is shown via a quick burst of light and a zeppelin in the sky appearing or disappearing in the sky.
In a third-season episode, Fauxlivia meets her fiancé at the aforementioned Empire State Building upon his return from assisting in treating a North Texas cholera outbreak.
While not entirely clear if The Secret Adventures of Jules Verne takes place in an alternate world, the heroes travel the world in an airship much more advanced than possible at the time. Then again, this isn't even the least likely invention in the show (hovering Time Machine, anyone?). A later story arc features a group of baddies copying the design into an even larger, armored airship complete with cannons in order to help the South win the American Civil War. The reasoning is that battlefield artillery is designed to shoot horizontally (which is wrong, especially if mortars are also used) and can't shoot an airship above.
Continuum features a certain future CEO that lives in a penthouse on top of a strange upside-down satellite/Zeppelin that should by all rights capsize immediately, but can fly upright because FUTURE.
Abney Park is a steampunk band whose fictional persona involves their plane crashing into a time-traveling dirigible, which they then commandeered. They have since become airship pirates.
The song Geni e o Zepelim ("Jenny and the Zeppelin" in English) features a villain that rides in in a giant Zeppelin and threatens to blow up the entire city.
Tabletop RP Gs
In a January 2000 Suppressed Transmission column, Kenneth Hite dubbed this trope "Hite's Law", and took it to its logical conclusion: our own history was an Alternate Universe in the early 20th century.
One of Ken's contributions to GURPS Infinite Worlds is a table to randomly generate alternate technologies for one's randomly generated worldline; it has a note that certain results dictate adding zeppelins regardless of the rest of the universe's tech level. Apparently, alternate history just generates airships.
Airship technology turns up from time to time in Shadowrun: in remote drones for aerial surveillance, in huge "cargolifters" for inexpensive bulk transport, and in luxurious cruise ships for the ultra-rich. The finale of the first Shadowrun book takes place at an airfield where a yakuza boss has just flown in on a zeppelin.
GURPS All-Star Jam 2004, a 10-chapter compilation of various roleplaying concepts and settings, devotes one entire chapter (by Brian J Underhill) to airships.
A favorite (if blatantly anachronistic) mode of transportation for the Sons of Ether, who for the most part revel in just the type of aesthetic that would spur mad scientist/mages to build large and improbable airships. Due to practicality (and Paradox), most zeppelins are found in off-world Horizon Realms.
Battletech has Zeppelins as support vehicles, in small, medium and even large. In addition, the Star League apparently once used a Zeppelin based design to create multi-platform flying cities.
In the setting of Space1889, most flying ships on Earth and Mars use "Martian liftwood" to stay aloft, giving them a more ship-like appearance. But on Venus liftwood doesn't work, so the German colony there is patrolled by Zeppelins — on another world in another world.
Persona 2 makes special mention of a model blimp mounted to the roof of the aerospace museum. Since rumors can become reality in this game, the fact that enough people suspect it's a real, functioning blimp makes it flyable. The launching of the blimp is a signifier that the basic rules of reality no longer apply.
The beginning of Arcanum: Of Steamworks & Magick Obscura sees the player barely surviving a terrible zeppelin crash. Interestingly, it seems heavier than air ships have a shorter than real-life span of use in Arcanum, as the before mentioned zeppelin was the first of its kind and on its maiden voyage, but was destroyed with stolen bi-planes (succeeding on one quest and providing proof the bi-planes flew insures their continued existence).
The Final Fantasy games love airships; each main-series game includes an airship in the mid- to late game as easy transport around the world. While many of the earlier games are simply sea-ships with propellers on, Final Fantasy VI and VII (both much more technology-oriented than their predecessors) feature actual zeppelins as their major airships, and Final Fantasy IX brings them back as general-use vehicles in a fantasy Steam Punk setting. (More recent games have airships so advances as to be barely recognizable as dirigibles.)
Used in Time Shift. Most of the game takes place in an alternate 1940s, so the zeppelins aren't so far out note In relality the last of the zeppelins was scrapped in April of 1940. The helicopters and giant mechanical spiders, however, make you realize something is more than a little wrong.
They are badass zeppelins. They have two giant vertical props, have two heavy-duty AA autocannon turrets, several machinegun emplacements, dedicated lift systems between decks, and self repair capabilities, thus able to fend off a heavy-duty assault by two or three dozen unusually slow jet planes.
The Crimson Skies game is alternate history in the Diesel Punk genre that has Zeppelins as flying aircraft carriers/battleships.
Rowan software's 1995 alternate universe flight simulator Air Power: Battle in the Skies takes place on a marshy continent with little in the way of roads and railways. Warfare is conducted mainly with aircraft and zeppelins. The player commands a fleet of heavily armed war zeppelins, including the aircraft carrier which serves as the main base for the player's fighters and bombers.
Command & Conquer: Red Alert 2 and Command & Conquer: Red Alert 3 (Both set in separate alternate timelines) feature the Kirov Airships, massive, heavily armoured war Zepplins used by the Soviet Union to bombard ground targets. Cutscenes and promo pictures, as well as the menu screen for Red Alert 3 show them looming ominously over US Cities. This is explained as an alternative approach to aircraft due to the Allies forbidding the Soviets from building a strong conventional air force. While the Soviets do get additional aircraft in Yuri's Revenge, this takes place after the main storyline, giving the Soviets more time to build fast-strike MiGs.
Wing Commander spinoff, Privateer 2: The Darkening, featured the planet Bex, complete with flying zeppelins and purple sky in its intro movie.
Dealt in Lead No zeppelins yet, but war balloons. During the American Civil War. No, they're not used for observation. They're used for wrecking entire cities.
Neosteam has steam balloons, which are basically hot air balloons with propellers (and possibly full of steam...). Unlike other transportation methods the balloons are free to use once you have bought a map.
An interesting detail is that rather than play a stock cut scene, the game remains interactive during the journey, so you can zoom in and out and circle around your character as s/he stands in the gondola while the actual terrain you are traversing unrolls below. The balloons can not be seen from the ground though.
Sky Gunner displays how different their world is by setting the first stage of the game around one.
The Panzer Dragoon series features a large number of various airships. Since you are on a dragon and could just run away from anything that couldn't keep up with you, it's natural enough that it needs a wide array of flying enemies, and since its a steam-punkish universe (with added magic) the vehicles of preference for the evil empire du jour are airships or airshipesque vehicles.
Syndicate's isometric view is explained as the player commanding the action from an airship floating above the level.
In Girl Genius by Phil and Kaja Foglio, zeppelin warships are the mainstay of the Wulfenbach Empire. The crowning achievement in airship construction is CastleWulfenbach, a literal floating airship city that easily dwarfs the typical airship.
And in print-and-online comic PS238, which counts as a parallel universe because it's full of superheroes, the distinctly familiar Von Fogg family's not-yet-seen zeppelin is an airborne independent supervillain nation.
ThisSubnormality strip has zeppelins become commonplace when time travel apparently results in the Nazis conquering the world.
Which is funny, considering that the Nazis were actually the faction that didn't use military or civilian airships whatsoever, scrapping them and turning them all into planes. It was the Americans that actually fielded over 170 airships during the war, to spectacular effect on Allied convoys.
Archer has the "Skytanic", and seeing as how the Cold War never ended, it's definitely an AU. Massively subverted in that the Hindenburg disaster did happen, and so Archer spends the whole episode convinced the dirigible is a massive explosion waiting to happen, despite the fact that it's filled with inert Helium. However, he also points out that despite its luxury, a relatively slow-moving airship with a single route is utterly pointless in a world of passenger jets. When arguing, he even points out the irony of building a floating vehicle that doesn't travel much faster than a ship. He's vindicated when the ship's captain is revealed to have placed a bomb on board because his employers lost his retirement package after going bankrupt. There's a Genius Bonus for informed viewers in the Captain's earlier defense of cruise airships, in which he points out that they outcompete ocean liners. This is true, but ocean liners themselves died out long ago.