@theww2lover For specifics, since I designed these from scratch imagining how each part might be made....

Electricity: basic Copper-Acid , the Acid is refined from lemons first, then other sources as innovation runs it's course (I'm not gonna give myself credit for inventing everything, there are other people making discoveries in this world)

Iron-source: black-sand beaches on New Zealand (the main Islands are the basis for the fictional kingdom of "New Sundaland"), as the kingdom grows trade is set up with Indian Kingdoms for their resources too

Engines: My first engine design (not used in Simple planes as it's physics don't allow it without the rocket-mod) is basically Hero's Aeolipile using fuel instead of steam, with internal combustion introduced once factories are made capable of such measurement specific-machines. The proto-jet in some of my models is basically akin to a radial engine with a huge Supercharger built around it, but a weakened and re-scaled J-15 does the trick for now

Fuel: coal for ships, naphtha from Egypt and the middle-east for Cars and planes.

Rubber: trees Taken from areas bellow the Mayan Kingdom and replanted in the pacific specifically for renewable harvesting, with other ingredients traded or mined as necessary.

I even attempted to make a rudimentary BVR (Beyond visual range) device for a night-fighter in this timeline (detected electromagnetic interference from aircraft-engines, using copper coils was my rationale, but it would take a lot of work to actually make happen, and I suspect in real-life the host-planes engines would cause too much interference)

I've never really had to write it all down before lol, but that sums up pretty much all I remember :) There's more info on the overall storyline on my other posts, and please feel free to message me any ideas for vehicles/inventions adhering to the story while advancing it, I love to receive inspiration :D

@theww2lover Answer:
A- it's part of a little what-if I made up a while back whilst fantasizing about traveling to ancient Rome (New Sundaland is the kingdom I kick-start, but I'm not much of a leader so I make government to do that while I invent) I have a reasonable knowledge of engineering and history, especially with regards to mid-WW2 aircraft and where to get resources I'd need to make these things in a pre-industrial environment so I design these aircraft based on that premise as both a backdrop and inspiration for my designs.
B- the story takes place from around 300AD, well within the iron age where inventors have already proven concepts we use today, including magnetism, electricity, and the first rudimentary engines.
C- it's a fictional vehicle so I could say "magic" and it would have the same weight.