Quinn was surprised that he was not the only aircraft engineer in the world. He also wasn't the best. There were several engineers down in the Underground who knew a lot more than Quinn, and they already had developed most of the schematics for a warbird made from ethersteel. And it was beautiful.

The first thing that Quinn noticed was that the designs included things called "flaps" that were mechanical devices placed on the inner wings. The purpose of these devices was to change the shape of the wing to lower the stall speed at the cost of efficiency. This was useful when landing because a safe landing at low speed was more important than efficiency.

Some of the engineers had even been hiking to the highest peaks and waiting hundreds of hours for tiny glimpses of the airplanes and fighter jets that the oculomancers use. Quinn didn't even know that the oculomancers could fly, that the flying machine even existed. But, they provided detailed sketches. And those sketches were even more beautiful than Quinn could possibly imagine.

There were at least six categories of flying machines that the people down in the Underground had managed to sketch. The sketches were the result of grueling hikes, some hundreds of miles long through horrible weather, in order to have a small chance of witnessing. The common Faithful around the Underground had all manner of superstitions as well.

The first category of aircraft had a single propeller and a high wing design. They typically were flown very poorly and were likely used as training aircraft for inexperienced oculomancers. The second category of aircraft was the double propeller design that was more stable and was likely used to ferry the oculomancers between the ground and the tops of the spire. The third category was that of the long tube-like craft with loud engines that were likely used to ferry the Heritors to the tops of the Spires for their secret meetings with the witches. The fourth category was the larger tube-like aircraft that were likely used to carry large numbers of oculomancers between spires. The fifth category was the arrowhead-like planes that flew so high that they could only been seen with a telescope, and were likely used for spying. The sixth category of aircraft were angular and predatory, and the engineers theorized that they only had one propose: fighting.

The design that they called the Warbird was a compromise. The oculomancers had access to some technology that they did not understand. That technology allowed the aircraft of the spire to fly very far and very fast and the engines made a lot of noise. The Warbird was an extrapolation of the first category, a single engine design, though the wing wasn't placed as high and the engine was more powerful. It was sleeker, more predatory, and capable of flying faster. In theory.

Quinn began to make contributions to the design. He learned the mathematical methods that the other engineers used. Lift, drag, stability, pitch, roll, yaw. He learned many new terms for communicating ideas with the other engineers. He also had a keen eye for safety problems, which made sense. His brother had died in a flying machine.

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The biggest problem was that Quinn needed to learn the notation that the other engineers used. They used a mix of different types of mathematics which they believed had not been modified by the oculomancers. They believed this because the base assumptions seemed self-evident and the proof by inductions were all verified and peer reviewed by multiple mathematicians throughout the caverns.

Quinn quickly realized that the most important aspect of engineering was communication. The notations that they used were designed to facilitate communication while also making it difficult for charlatans to copy the format and produce pseudo-science or pseudo-math. The fact of the matter was, any flying machine was going to kill the pilot if the engineers designed the aircraft wrong. So there was no room for getting things wrong.

Over the next few months Quinn found himself designing mundane, but important, aspects of the aircraft, such as the gunsight, the anti-icing system, and the landing gear redundancy systems. It taught him a lot about engineering. The engineers working there had seem some horrible things, just as Quinn had. They just had more tools to prevent those horrible things from happening again.

Quinn began as a junior engineer, but he was shortly shifted far away through the caverns to a less competent workshop. He suddenly became the senior engineer in the room, teaching others about the proper notation for communicating ideas and making proofs. Ultimately, the goal was to avoid charlatanism, Quinn understood, but the younger engineers did not understand this. They wanted to be told what the right answer was.

But the sky didn't have right answers. It offered only the blood-price of being wrong. Many professors can pass out bad grades, but professors generally do not kill their students and remove them from the sample when they are wrong. It was unfortunately impossible to convince the more junior engineers of the danger for the pilots.

After being shuffled around to various workshops and making various contributions to the design of the Warbirds, a final design was sent to him for review. He was locked in a secret location with the design, deep in the caves. The designs were probably an aggregation of the ideas contributed by multiple workshops.

The final design as a tail dragger, with a small wheel on the tail and two larger wheels near the front that retracted into the body through mechanical devices. The airplane was equipped with an anti-ice system, flaps, machine guns on the wings, a gunsight, and a propeller powered by an advanced ethermancy-powered radial engine. Quinn's design improvements were significant, though he understood he was standing on the shoulders of giants. The design as it existed before he arrived was quite good, and he learned a lot about airplane design.

The schematics were sent to various factories throughout the cavern network. They sure loved redundancy. There were a dozen factories making the components and assembling the airframes. The actual airframes were finalized in large chambers inside of caverns with one open cliff where they could be hoisted up and then flown over the edge of a canyon. Many young men volunteered to become pilots on the craft. The Primarch had declared that anyone who died in a flying machine would have their soul instantly travel to Paradise.

War was breaking out with the Blue Wolf of Nydia, Sasha Varelion. The armies of the Theocracy stood at the ready. Battle was on the horizon, the the Theocracy had a surprise waiting for the Blue Wolf woman. The Aethersteel Warbirds, an ill omen of death for the soldiers of the Empire.