Southwest Airlines has bid $170 million to take Frontier Airlines out of bankruptcy protection.
A bankruptcy court auction for Frontier is set for Thursday.
A Republic spokesman says the carrier will be present at the auction -- but airline officials are considering their next step.
Frontier's route network looks like a spider, with a body in Denver and about 50 legs to cities around the U.S. -- plus Mexico and Costa Rica.
Southwest already competes in Denver with Frontier as well as United Airlines, which has a hub in Denver.
Southwest says it would keep all of Frontier's current markets, including Atlanta -- one of the last big markets where the low-cost carrier doesn't currently fly.
A Frontier spokesman declined comment.