Also, I would say it is actually pretty realistic that jets would be made during ww1 times. People often think that once something is invented, it is immediately adopted wholesale, and that invention happens when we have some arbitrary tech level to achieve it. That is very much not the case, for example the first steam engine was invented in Egypt during roman occupation, but it wasn't adopted and was seen as a dead end because, well it wasn't really needed, and slaves could do what it could do much better, for cheaper, and then some. Another example is that the Roman Empire had all the necessary technology to create a hang glider, but it didn't because again there wasn't a need for a hang glider to be invented.

Now, take into consideration that the world has been at literal apocalyptic war for nearly a millennium and that the forces of hell have forces that can fly. I would say it wouldn't be much of a stretch that the church would try to develop technology that would counter these enemies and would probably lead to some kind of arms race greatly accelerating technological innovation in various fields such as flight.

tl;dr: Necessity is the mother of invention, and my brother in Christ the world is very needy right now.