Apparently "Spirit Airlines" (Australian version) has also registered the domain
spiritairlines.com (currently not functional), but Spirit Airlines (US version) had a problem with that:
http://arbiter.wipo.int/domains/deci...2001-0748.html
If you
whois the domain (spiritairlines.com), you'll find an administrative contact, and his e-mail address. You could always write for an update.