Doglike animals (hydrogen sniffers) are briefly described being harmed and killed in battle, though none are named or plot-relevant. One image depicts a deceased hydrogen sniffer in the background.
No animals are intentionally abused, though several are harmed/die in battle, and there is a mention made near the beginning of using a whip near draft animals, although it is unclear whether they are struck or only reacting to the noise.
Some unnamed characters die in an airship fire, and there is an image of this event from far away, though nothing is described graphically. It is also mentioned that a main character's father died due to fire, though again, nothing is described in detail. There is one additional image of an indistinct figure in a burning plane.
A female character has to disguise themselves as a male in order to go into the army, so they are referred to as he/him and as a male by everyone who knows them as that, but she/her by the people that know about their real gender.
Glow worms appear, though mostly only mentioned in passing, and some animals with insect-like qualities are briefly described, but there are no bug-focused scenes.
No intentional abandonment. One of the main characters is left at home while his parents are on a trip, however, and (spoilers) they die and do not return.
Both of one of the main character's parents are killed, though he is not present when it happens and it is never described graphically. The other main character's father dies before the events of the book. Reference is made to both throughout the book.
Yes- air battles take place in this book, and several planes are brought down, though the actual crashes are not described. An airship also crash-lands, and named characters are wounded in the accident, though none die. It is implied that some unnamed characters die. A separate airship also catches fire and crashes, and while it is not described too graphically, it is assumed that there are no survivors. No named characters are harmed due to this accident. There are images of the burning airship and of planes being taken down in battle.
At the beginning of the book, one of the main characters follows several adults after they lie to him in order to convince him to come along with them, and they do effectively abduct him, although their motives are to remove him from a dangerous environment, and he is never in any actual danger from them. Later on, the same character is detained by a different group, and briefly held at knifepoint, although this turns out to be a ruse, and he is never harmed or in real danger during this time.
Some unnamed characters are involved in non-graphic plane/airship crashes and are implied to have died. Another unnamed character falls off a horse and is killed.
A main character is knocked out via the use of drugs near the beginning. Later, another important character receives a head injury, and is briefly unconscious. Neither suffer lasting ill effects.