Musing on the opening sequence in The Goblin Emperor:
What does the existence of the other passengers on the airship mean for Csevet's intended route to and from Edonomee?
Event sequence-wise, the Wisdom of Choharo crashes on the morning of the 20th. The crash is discovered sometime after noon, and the Lord Chancellor writes his letter to Maia informing him of these events before midnight the same day. Early on the 21st (Maia is asleep, Setheris is still awake, and Csevet refers to the crash happening 'yesterday'), Csevet delivers the message to Maia. Their return trip to Cetho takes a mere 2 hours, which would suggests that the ship Csevet took either left very late at night on the 20th/in the first hours of the 21st, or else that it didn't travel direct from Cetho to Edonomee (left sometime earlier in the afternoon/evening of the 20th and made other stops between Cetho and Edonomee).
We hear at other times that Maia has always lived far from all but the smallest villages (though there must be a village of some sort near Edonomee, since the female staff live off-site and there are additional non-permanent-staff workers hired to help with the grounds at times), so the idea that all of these extra couriers/mazei/missioners come aboard in The Village Near Edonomee in the middle of the night seems unlikely. And while I could see an urgent message like 'you are now Emperor because most of your immediate family just died' being delivered in the middle of the night because of urgency, the presence of all those extra people precludes this being a one-off flight scheduled purely to get Csevet to Edonomee with the letter for Maia as soon as possible. Not to mention the fact that "send an airship to tell the VIP what just happened and put it at his/her disposal to come to court ASAP" is a thing that Chavar apparently does for the princes and archduchess, but explicitly doesn't do here for Maia.
This leads me with two possibilities:
There is a regularly-scheduled overnight route from Cetho to unknown points west, and Csevet got on it because it went closest to Edonomee, so they added a stop this time. Since the ship was still available for Maia to commandeer (rather than dropping off Csevet and then immediately leaving), I assume that the intention was for Csevet to get back on the same ship, which would either loop back to Cetho at the end of its run, or else drop him off somewhere else on the route where he could transfer to an east-bound ship.
This was not a regularly-scheduled trip, but since an airship needed to be sent out to Maia at Edonomee, all the couriers and officials waiting for the next west-bound ship got aboard so that they could be efficiently dropped off after Csevet's mission was completed (and, as before, the ship waits for Csevet - though in the absence of regular routes, I would assume this ship loops back to Cetho after dropping off those passengers and picking up any officials with business at Cetho that are waiting other stops along the way).
Of the two, I'm leaning towards the first. In part because airships are supposed to be for fast government business (and just keeping everyone on standby indefinitely seems very inefficient, you'd be better off sending them on ground or water transit unless airships stop by with some frequency); in part because of the reference in The Grief of Stones to an upcoming airship departure from Amalo to Cetho suggests that regular flight schedules are how they operate; and finally, because sticking Csevet on the equivalent of the all-night stops-at-every-little-town bus exactly matches the level of petty stalling and undermining that Chavar displays towards Maia. Constantly.
In the next same vein, how long did the Lord Chancellor wait before sending his letter to Maia? I don't think we can really get this down more closely than 'between noon and midnight on the 21st'. The fact that the initial report only says that the Wisdom of Choharo crashed between sunrise and noon (which is a wide enough time-span that I imagine it refers to the time difference between when the ship left Amalo and when the crash was discovered. They don't seem to have remote communication that would allow a ship to contact ground control, but assuming someone knows when the Wisdom left Amalo (and surely lots of people did) then simple math with the usual speeds of airships and the distance between the crash site and Amalo should give a much narrower window for when crash occurred. Six hours, after all, is three times the travel time from Cetho to Edonomee, and while we don't have a definitive scale map of the Ethuveras, the map and travel times we do hear of suggest that six hours in an airship is a substantial distance relative to the size of the country.
Even so, our two extremes are thus that the Lord Chancellor found out about the crash in the early afternoon and immediately wrote to Maia, or that he wrote the letter very late on the 20 (whether because he put off writing the letter as long as he plausibly could, or because it took that much time to sort out what happened.) Allowing that it would take time for reports of the crash to reach the court, and that the Lord Chancellor would probably want to be very certain before informing Maia that he was Emperor (I can't imagine Verinechibal or any of his surviving sons would look kindly on the Lord Chancellor rushing to act on an incorrect preliminary report which turned out to be wrong). At the same time, given how helpful he otherwise isn't, I could also see this Lord Chancellor taking his time to make absolutely certain that the other heirs are, in fact, all dead--and then a small breakdown coming to terms with the fact that a complete nobody is now Emperor--and then also putting off sending that letter until the very end of the day so that he can avoid dealing with the new Emperor as long as possible without openly causing a deliberate delay.
All that long paragraph is to say: while I think the 'letter written very late in the day' direction fits the story best in the Lord Chancellor's timeline, I think the presence of those other passengers fits marginally better with an earlier time and a regular route. Perhaps an afternoon/evening departing flight that's supposed to take 6 or 8 hours looping through the western provinces, stopping at set places to pick up and drop off passengers (or following a set route and stopping only where a passenger needs to get off, or where some signal indicates passengers to pick up). A not-regularly-scheduled stop at Edonomee near the end of this loop could put Csevet there in the middle of the night just before the ship is meant to return home (and would mean all those passengers where only delayed a few hours on their trip to Cetho, not taken in the wrong direction entirely). If the flight was specifically built around Edonomee, it would presumably be the first (most important, if not closest to Cetho) stop, and all those passengers might well be going back the way they came when Maia gets onboard.
Third and final point of musing is: what would a respectful Lord Chancellor have done in place of Chavar? Based on the reference to airships being put at the disposal of the Princes and Archduchess Nemriän, "send an airship with the news and have it wait to take the VIP and their entourage to court" seems to be the general plan. This is mentioned in Chavar's letter of the 20th suggests that the airships are or shortly will be underway at that time; again based on our rough knowledge of the country's size and few datapoints about travel distances, I think we can expect those airships to arrive at their various destinations sometime during the 21st, and that something between a few hours and a whole day will be needed to get the ship ready for its return flight and for the VIP to get ready for the trip (since the 23rd is the earliest that all these people can be expected to be at court and ready for a ceremony).
Additionally, considering the mores of real-world royals, I'd expect someone of higher rank than 'random courier' to deliver such important news to a new Emperor. Is that the sort of thing that Chavar would be expected to do in person? If he's personally needed to keep the government running at this moment, surely another very high ranking government official would be selected in order to make sure that the message got to the right person and to show respect to his new status: perhaps one of the Corazhas, or a very high-ranking noble at court, or even another member of the Imperial family. For that matter, there could well be a delegation representing the different power centers, all jealous of their prerogatives or eager to make a good impression by being the first to swear loyalty to the new ruler in person. And surely, they're bringing the new Emperor's security detail along to immediately take up their duties. Maybe, if the decision-maker is conscious of the low budget and general living conditions at Edonomee, they even send along some newly-recruited edocharei and a hastily assembled mourning wardrobe to prepare the new emperor for his journey to court.