Inter-sphere Travel

Since the introduction of Law of the City-Sphere Kaun involving magitech usage, almost all travel in between Kaun and other city-spheres has been grounded. This is both for the safety of the capital Tyro, and for the safety of merchants and tourists.
Authorities in both Kaun and Tyro initially grounded flights via Kaun over concerns that they would be next attacked as Magical Criminal Activity rose.All merchant flights were then rerouted via Tyro , instead of stopping at Kaun as they had done previously. Permits are now able to obtained for travel to Tyro, in order to travel from the capital to other city-spheres. These, however, are expensive and given under extreme scrutiny. As such, travel is limited to essential supplies, ambassadors and civil servants, and the very rich, who usually don't desire a trip to the smog-filled Kaun. 
Black market  trips are known to operate, with travellers bundled into compact spaces among the trade ships. These too are expensive, with payment in a combination of risk and debt.