The Associated Press

DALLAS (AP) -Southwest Airlines Co. is seeking to trump a rival bid and acquire Frontier Airlines, a Denver-based carrier operating under bankruptcy protection.

A court had already approved the sale of Frontier Airlines Holdings Inc. to the parent of Republic Airways for $108.8 million, but that deal can be nixed if a better offer comes along.

Dallas-based Southwest said it submitted a nonbinding bid of $113.6 million. Southwest hopes that making the bid will allow it to talk with Frontier and get information to help shape its final proposal.

Southwest said it faces an Aug. 10 deadline for submitting a binding bid. If there is more than one qualified bidder, an auction will be held the following day.

"We are excited about the opportunity to submit a bid," Southwest CEO Gary Kelly said in a statement. "We see a strong fit between our company cultures, a mutual commitment to high quality customer Service, and similar entrepreneurial roots."

Southwest recently went back into the Denver market, where it competes against Frontier and United.

Shares of Southwest rose sharply on the news. They were up 33 cents, or 4.4 percent, to $7.84 in afternoon trading.