Most of the visible contrail seems to come from engine emissions, though you can also see condensation effects purely from the dynamic pressure changes around t

Most of the visible contrail seems to come from engine emissions, though you can also see condensation effects purely from the dynamic pressure changes around the plane. Those are more obvious with fighter jets and acrobatic planes though, where they are generating more severe aerodynamic effects rather than sustained level flight. Assuming the visible contrail correlates well with the part causing climate effects, an electric ducted fan might be a big improvement, by removing the combustion emissions. I don't know if some other fuel-burning engine could be combined with a ducted fan and sufficient emission controls to also serve this purpose.