Aerostats

It's certainly a beautiful sight, to be above the clouds. You can get lost, just gazing into the sky, at all those stars, forming foreign constellations above this bizarre world of ours. Unfortunately, getting lost gazing at the sky means that you aren't paying attention to the time. Now imagine my surprise when I descended, thinking myself right on time, only to be met by the harsh spires of Antillia rather than the shingled roofs of Tremontaine.

— A very foolish and very lucky Aeronaut

Aerostats, or more simply hot air balloons, are lighter-than-air aircraft which are often employed to carry people between islands on the Pariah's Tides. They provide an alternative to sailing ships, which are forced to travel on the surface of the dangerous Tidal waters, and are thus subject to all the dangers which can emerge from those dark waves. Travel via balloon, on the other hand, is a more safe, albeit less precise method of travel.

Introduction to the Tides

The aerostat was introduced to the Pariah's Tides when Jean-Pierre Blanchard, a French aeronaut, was blown out to sea during a pleasure flight. He ran into a storm, and though he managed to survive he had gotten himself stranded in the Pariah's Tides. His balloon, punctured and descending rapidly, was spotted off the coast of Shackamaxon and he was quickly rescued. His aerostat had been destroyed, both by the storm and his subsequent descent into the Tides, but his rescuers still brought its remains on board.
Blanchard was brought before the Fathers, and explained to them just what the aerostat was. While it was destroyed, Blanchard was quite knowledgeable of its workings, and explained to the Fathers that the balloon uses fire to heat the air inside of the large envelope, which makes the air inside the envelope buoyant and causes the balloon to rise. Intrigued, the Fathers ordered that a balloon be built according to Blanchard's specifications. When the balloon was complete, in true Father fashion they ordered that Blanchard be the one to test it out. To their surprise, it was a success, and Blanchard quickly rose into the sky. He disappeared above the clouds, and was not heard of for several days. However, less than a week after his disappearance, he washed up on the shores of Empire Island, half-starved and half-drowned, but alive and very clearly not where he used to be. This piqued the interest of many Americans, who decided to pursue the concept of the aerostat further. Blanchard was paid for his troubles, and four years after his initial appearance on the Tides, he was caught in another powerful gale while ballooning and was never heard from again.

How They Work

As it turns out, Blanchard had been very lucky, to land close to an island not just once, but twice. The shifting of the Tides is completely random, or at the very least the patterns it follows are so bizarre as to make it effectively random. He was just as likely to land in the open jaws of a whale as he was to wash up on the shores of Shackamaxon and Empire Island. When one ascends above the clouds in an aerostat, they effectively "leave" the confines of their island. That means, whenever the Tides shift, they are no longer dragged along with their island. They are free to drift, above it all. When they descend, they again have a fixed position in the Tides, and move along with their shifting. This unique ability means that aerostats are capable of allowing one to travel great distances in a very short time, as long as they are lucky.
Of course, luck isn't exactly very reliable. No one would be willing to take a method of transportation that relied entirely on it, since a bad streak would almost certainly mean death. Luckily, one doesn't have to rely on luck when a navigator is on call. The clairvoyant abilities granted by prophet-sap mean that navigators are capable of predicting where the islands of the Pariah's Tides will be, and when. This allows them to figure out when another island will end up more or less lining up with the current position of the island they are on. Though this is not an everyday appearance, it isn't as rare as one would expect. The Tides shift often, so an occurrence such as that is bound to happen every now and again. When it does, a trip on a balloon can be a much more pleasant experience than having to brave the deadly Tides.
However, because of their small carrying capacity, balloons are not nearly as popular with anyone except for the wealthy. The wealthy can afford the expense of the crafts, as well as the best navigators who will give them accurate ascent and descent times, so that they do not end up lost. However, since there is still some risk of getting lost regardless, as well as being blown off course if one gains the ire of the Winds, aerostats are approached with some amount of trepidation even by those who use them most often. Because of this, they remain a niche method of travel, overshadowed much more reliable—if not particularly safe—ships.