What is the lowest, most basic technology level needed for a human population to be able to develop a reliable flying machine capable of transporting people over medium-short distances (at least a few kilometers)?
I have a setting where the world has no solid surface and is instead made of floating islands. I want to know if humans, given the need to move between islands, would be capable of developing flying machines early enough for the purpose of the setting.
There are no flying creatures capable of transporting humans across islands.
Whatever materials are needed exist in the starting island in their natural raw forms.
Humans are extremely motivated to leave the starting island and are actively working on a way to achieve this.
As for magic, there is an elemental system with seven elements: water, air, fire, wood (and flesh), stone, metal and a special seventh element. Humans can create the first six with the help of the seventh at the expense of their stamina.
For example, a human has a piece of the seventh element that is tuned to fire, they can create fire by channelling their energy through it. Using too much energy and the person passes out there and then. This element can also store energy for large periods of time, meaning it can be charged in preparation for heavy usage.
The specifics are quite a bit more complicated, but suffice to say that it can be used for powering an engine provided that the technology allows building an engine in the first place.