Lynn's sword ultimately paused in mid-air, because it wasn't hard to verify Nu'er's words, they just needed to have Laud ask those "whistles" again to find out if the bounty had been withdrawn.
That is to say, it was very likely that the inside of "Bloodthorn" already understood the manufacturing method of airships, but it was uncertain whether they had figured out that the thing relied on a gas inside the balloon, lighter than the density of air, to float up.
Although it seemed not difficult to discover this, the mainstream flight theory in the Wizard Land relied on thrust for takeoff, or on using Shaping Magic to imitate the flight of birds.
Although elemental wizards from the School of Elements had long discovered these gases, hydrogen, helium, neon, ammonia, and such, their buoyancy, considered individually, was extremely weak.
