Alexander has taken a slightly different approach to the building of their military might in the air. The knowledge and skill necessary to build sky fortresses is in the hands of Grunburg alone.
The only sky fortress that Alexander has was one built by the mages of Grunburg for the defense of the southern city. In exchange, Alexander will provide fresh fruit and meat products to feed the Grunburg airmen as long as they possess the fortress, a steep price at best.
Alexander uses this as a command station from which they can coordinate their defenses in the event of an air attack. From here the blimps and airships of all types recieve messages through the use of flags and scrying devises.
The elementalists building the airships of Alexander have far exceeded the skills of Grunburg ship designers and manufacturers. In exchange for badly needed lumber products from Geyon, Alexander supplies their northern ally with skyships.
The Alexandrian ships lack the quick manuverability of those manufactured in the Grunburg factories, but they can take a pounding like no others, a definate advantage with the advent of smoke powder and incindiaries. The ship are made from steel plates over an iron frame. It takes a lot to punch a hole in its sides, and if it does, fires are easily contained.
These ships were designed with air attack in mind as well. Large doors open up on the underside, where boiling oil can be poured down or incindiary devices dropped. Members of the Grunburg council are pushing to purchase more of these ships for attacks on the Broken Arm League, the eons-old enemy of Grunburg and her allies.