The constant search for new airship designs would seem to suggest that the previous ones crash with depressing regularity.
Front cover quote: "Suddenly, as they came out into the open, a cry went up from Pomp. 'Golly, Marse Frank! Dere am de airship comin' fo' all it is worth!' This was quickly seen to be the truth."
"Marse" being a way to say "Master," I suspect.