There’s nothing more iconic for a retro-future or pulp game than the addition of airships to the skies of your universe.  These elegant giants are romantic and nostalgic — a macro for setting the scene.  (Although I have seen some complain (fairly, I think) over on io9.com that they are a lazy means to set your movie/book/campaign apart from reality.)

A key to using airships is to realize the realities of dirigibles.  They are massive, yet very fragile.  Gunfire is unlikely to do a lot to them, but they don’t provide much cover from fire if you’re inside.  Incendiary bullets, if the ship is running hydrogen as lifting gas = bad f@#$ing day.  But a helium buoyant vessel is unlikely to be taken down by machinegun fire.  Bullet holes simply do not allow enough of the lifting gas to escape to disable the craft quickly.

Airships are somewhat susceptible to weather.  USS Shenandoah was destroyed when she ran into a double squall line over Ohio and was tossed up and down at  rates of climb much higher than her ability to valve gas and relieve pressure on her balonets (the bags holding the gas.)  She broke up, but most of the crew survived and free ballooned the two halves of the ship to the ground.  The year before, she had been torn off her mast by a hurricane and survived the experience with minimal damage.

The use of hydrogen was seen as a major issue for the airship, but most of the German commercial vessels saw no troubles due to the use of the explosive gas; they had extensive regulations for not running through storms that would create strain on the gas bas or create static on the hull (ignored in the case of Hindenburg), they did not allow smoking (save for a special room in the same airship.)  Hindenburg actually landed on the chimney of a house in Brazil in her first season of operation.  A lit one.  The ship didn’t explode.  Graf Zeppelin never had issues with fire.  Neither did R.100 –a British airship that ran flawlessly for several seasons.

Americans had no troubles with hydrogen.  They were a major manufacturer of helium, and US dirigibles floated on the noble gas.  (It was, however, expensive – $150/ cu ft. compared to $1/ cu. ft. of hydrogen…hence why the Navy got cheap and halved the number of values on Shenandoah, ultimately leading to her destruction.)   American airships were hampered  by other technologies.  These vessels were more practical, early on, than an airplane, and their development outpaced the instrumentation and design philosophies that would have made them safer.  Barometric altimeters gave incorrect altitude readings, and in the case of USS Akron accounted for the destruction of the ship when it flew into a storm — lower pressure gave a false higher altitude reading and the vessel, while trying to climb had no altimeter at her tail — at 900 or so feet long, the tail was much closer to the ocean and the ship foundered when she took on water at the tail.  Her sister, Macon, was destroyed because Goodyear hadn’t thought to run the tail through in a single cruciform, as the Zeppelin Company did.  In a high crosswind, the tail became a big airfoil and tore off.  The ship might have survived that, but the control lines to the rudder tore the lifting gas bags at the aft and the ship dropped like a stone.

Here is the major issue of the zeppelin:  weight.  Like all aircraft, they have limitations in how much the can carry.  Granted, they carry tons of material, but rain on the hull can reduce her lifting capacity by a ton or two.  Hitting the ocean with your tail increases the weight of the ship dramatically.

The British had terrible luck with their airship program from a combination of government micromanagement of design and construction (R.101), but they also had a cadre of commanders that did not understand the airship was not a ship.  It wasn’t made of wood or steel and mishandling them could do catastrophic damage (sort of like the difference between your crumple zone enabled automobile and old steel cars…  One of their commanders had a propensity for running their airships up onto their moorings too quickly and damaging them…but he was aristocracy and his connections kept him at the conn.)

Here are some excellent resources for learning about airships, how they handle, their strengths and weaknesses:

Pretty much anything airship historian Douglass Robinson wrote, but specifically “Up Ship” for the US Naval airship project and Graf Zeppelin and Hindenburg for the later German vessels, and The Zeppelin in Combat (which is concerned with WWI vessels, but gives an idea of the problems of airship combat.)

Smith’s The Airships Akron and Macon (US Naval Press) is excellent, as is Althoff’s USS Los Angeles.  Archbold’s Hindenburg: An Illustrated History is a lovely coffee table book that is good for allowing the players to get the feel for these craft.  Higham’s The British Rigid Airship is another excellent resource on the entirety of the UK Airship Scheme.

Online, The Airship Heritage Trust has a nice website on the British program, with some pages on the German and American ships.  The University of Colorado has a site here.  US Naval airships are discussed here and here.  The US Navy has more on them at their historical site (search airship.)