Aircraft for Safehold

That would require solutions to engines and airframes.

There have been diesel aircraft.

Wood was a successful material for a long time but hopeless if Charis wanted aircraft carriers. Aluminum without electricity would require expensive refining. A leapfrog to composite materials would do it but might be hard to figure out without Merlin being too blatant about supplying information.

The Wright Flyer was fabric and wood, but it was an extrapolation of existing glider designs. I haven't seen any indication of gliders on Safehold, so where would the initial idea come from? Yes, I know Merlin could seed it easily enough, but he's spent the past 10 books trying to establish that everything he's helped Charis produce is coming out of native Safeholdian ideas and inspiration to avoid any question of "demonic influence". I don't see him changing tactics at this point.