Actually, it is mentioned on page 234 of Eberron: Rising from the Last War.
There isn't a reliable way for a non-heir to control a ship, at least at low levels. You can control a ship for 1 minute by making a DC 20 Charisma (Persuasion) check, but the only people that can make that automatically are 11th level rogues with Reliable Talent and at least a +10 to Persuasion. You could also use
charm monster or
dominate monster, but that is dependent on whether the elemental makes the saving throw. So, only Dragonmarked members of House Lyrandar are flying airships, and you need two of them so the ship can fly constantly (even then, it's a 12+ hour workday for each of them).
We're starting a campaign that includes a PC member of House Lyrandar, and a prototype Cyran airship they found at the edge of the Mournland right after the Day of Mourning. The PCs were all part of a mercenary unit that claimed the airship as spoils of war, and it's going to be interesting to explore how House Lyrandar will react to it. The ship is a tiny scout vessel, barely large enough to hold the group, and possibly the smallest airship ever created (I just ordered
this to use for the game). The OOC reason for it is to give the PCs an easy way to get to far-flung locations for adventure without taking ages to get there. Yes, that means we're bypassing several potential lightning rail plots...though I could see something like The Train Job episode of Firefly.