but only just noticed faint aerodynamic contrails coming from the wing flaps.
Yes, in high humidity conditions this is quite common. Strictly speaking, in terms of the definition of 'contrail', though...these are more a type of compression vortices (if I can "make up" a term). Airflow dynamics that compress the air, and the moisture in that air then condenses "out" of the vapor state, and becomes visible.
The airflow dynamics flowing off of the trailing-edge flaps (proper terminology) account for some interesting visual effects, in certain atmospheric conditions.
EDIT: I won't post images that I personally did not take, since against the "spirit" of this thread topic...but a perusal of YT (and elsewhere) will find countless stunning video and still pics of amazing "compression vortices" (
tm pending!

).
Look for some of the high-bypass engine fan blades (the big ones that are most visible, what we call the "N1" fan), in large jet engines, inside the cowling...phenomenal.