Airships are phenomenal pieces of manatech invention, having been around for quite awhile, but changing very little through time due to their inherently near-perfect design. Airships can carry an incredible amount of weight between Spheres without needing to refuel mid-flight no matter the distance, and using a relatively small engine comparative to its carry weight.
Airships can vary radically in shape and size, as well as design and ultimate purpose, but all possess a key feature; seatbelts. Due to the existence of the Gravity Threshold Distance on Spheres, airship travelers ultimately must face the event in which gravity switches between that of the Infinite Ocean's and the Sphere they are leaving/approaching. Passengers must seat themselves and buckle up when the airship passes through the GTD, whereupon they can move freely about the airship once it has oriented itself properly.
Airships run on liquid mana and gas mana, depending on their position relative to a Sphere. Because gaseous mana is extremely thin close to Sphere surfaces, airships cannot run purely on gas mana when lifting off from a Sphere or touching down. Liquid mana burning in magitech engines is used to get the airship initially away from the Sphere (generally switching to use of gas mana when passing the GTD), before running on gas mana. Due to the innefficiency of using liquid mana for airships in general, it is limited only to liftoff and touch down for airships, and rarely if ever used to fuel the airship during the remainder of its flight.
Because gas mana is endless in the skies between Spheres, airships can theoretically run for an unlimited amount of time when using gas mana.