Frontier filed for bankruptcy protection in April of 2008.

Republic Airlines is owed millions by Frontier and put up an initial bid of almost $109 million.

Southwest, which has much deeper pockets, bid $113.6 million.

The auction considers others factors as well.

The impact on creditors, Frontier employees and the community will also be taken into account.

“It’s a very complex mix,” said Frontier spokesman Steve Snyder.

“It is not a specific mathematical equation for figuring something like this out, which is why we caution people about speculating on the ultimate outcome,” he added.

If Southwest wins the auction, it is widely assumed that Frontier would be folded into the company’s operations.

Frontier management says customers should feel confident booking tickets through next summer, and the CEO has written a letter to employees asking them to ignore the speculation and rumors.

Sean Menke wrote,“I need you to focus on running our airlines safely and efficiently and on providing our customers with outstanding service like never before.”