As a woman, ex-structural analysis engineer at a very large, american, plane-making company, I have a couple of follow-up questions for you:
1) What is the age of the person who is interviewing you, and what is the general age of the other employees at the company?
2) What is the gender of the person interviewing you, and what is the gender composition of the company?
3) What is your age? In my opinion, if you are older/more experienced, you can get away with dressing down a little compared to a < 30-year-old, though that doesn't apply as universally to women.
4) What area of the US are you in? East coast is far more formal than west coast, in my experience.
5) What industry is this in? For example, software is very, very casual in dress code but biomedical researchers that may work closely with doctors/hospitals probably don't wear videogame tshirts to work.
When I interviewed for my first engineering job out of school I wore slacks, leather shoes, and a nice button-up. I did not wear a full suit, but I was just one step down from that. If I were to interview for that same company at my current age, I'd still go to at least slacks (not khakis) & a button-up, which some people classify as "business casual," but I've always found that term far too vague when considering women's clothing.
Depending on the company you're interviewing with, wearing a full suit can actually be a detriment, since it can make you seem like you don't know "the way it is around here," and you're "too stuffy" or "too businesslike."