Current versions of aircraft realism only require a very short runway (when runway requirement is on) before the plane takes off: around 4 tiles with the jet + rocket fuel. I remember using this mod in the past and it had a much higher requirement (on the order of hundreds of tiles): is there any way to get this behavior back on the new version? I tried tweaking various settings but nothing seemed to affect it.

You can adjust the required runway length by changing the "transition speed" under the settings for the Aircraft mod (not Aircraft realism). A higher transition speed requires a longer runway to reach the speed for takeoff.

Those don't seem to be changeable in the settings menu, since the allowed range for the field only encompasses the default value:
https://imgur.com/a/MzoZBdf

This is something the Aircraft mod author needs to fix, I reported this to the Aircraft mod author for you