As for skirts, if the fabric is loose enough, they are just going to sort of wrap it around the leg and pat it down. If the skirt is tight enough that fabric can't be wrapped around the inner leg, you might be looking at something a bit more thorough. If at any time a TSA officer is placing their hand up your skirt, and you are not dating them, then they are performing the search incorrectly. Notify their supervisor, it shouldn't be allowed.

TSA says that during the new standard pat-down, a screener of the same sex will examine your head, shirt collar area, and waistband, and may use either the front or back of his or her hands to feel your body, including buttocks, around breasts, and between the legs, feeling up to the top of the thigh. Women in tight skirts that don't allow an agent to feel the thigh area may be asked to remove the skirt in a private screening area and will be given a gown or towel to put on.