There was a meeting a couple of years ago between my company's engineers and some NASA representatives. No one in my company really wears suits anymore and the NASA guys complained that it was "unprofessional" to not wear a tie when one of our leads went up to present in just a Tshirt and jeans. After hearing that, the lead went back to his desk and came back with a wooden joke tie hanging around his neck to continue. They stopped criticizing our apparel after that.