Despite the pleas by employees  to preserve their airline, there's no guarantee that Frontier  as we know it will continue to exist. Dallas-based Southwest Airlines has until 10 a.m. this morning to submit its formal $113.6 million offer, a few million more than what Republic Airways Holdings has put up. If successful, Southwest would eliminate a major competitor at Denver International Airport and gain flights in markets that include Mexican resorts, according to The Denver Post . As aviation analyst Mike Boyd of Boyd Group International in Evergreen points out, Frontier has given Southwest "a bloody nose and a lot of heartburn" since Southwest entered the Denver market three years ago. Meanwhile, if Republic gets Frontier, Bill Swelbar, a research engineer at the Massachusetts Institute of Technology's Center for Air Transportation says it would create "overnight, a new, potentially threatening competitor to Southwest's domestic dominance." The Houston Chronicle  writes that Southwest seems to want Frontier to prevent anyone else from buying it. And The Street  opines that Southwest's bid "may be viewed as a sign of its failure" in the market.