Spirit Airlines is adding another caveat to flying with the ultra-low-cost carrier — a more stringent dress code. On Jan. 22, Spirit updated its contract of carriage to specify fashion faux pas that could leave certain customers grounded at the gate. The airline may bar passengers who are “barefoot or inadequately clothed … or whose clothing or article, including body art, is lewd, obscene, or offensive in nature; or has an offensive odor unless…