This might be a little "picky" of me! ?? The airlane between Sanzley and Osbenleyw appears to bypass closely by the Nexus at Mallenbring. I would imagine that the nexus lines would naturally be attracted through each nexus (or generated by them?), constraining flight paths to those avenues. On the mundane level it also implies that there is no "service" between Mallenbring and these two other points -
"Single first class non-stop to Mallenbring please",
"Sorry sir, you have change at Waibenly, a free terminal rickshaw service is available!"
I guess much is dependant on the "physics" of the nexuses - be they natural locations or manmade constructs an so on.
I need to think about air travel in my RQ campaign I'm working on, the Godlearners can get up to some weird stuff....