Southwest Airlines Co., the third-busiest carrier at Denver International Airport, keeps losing money. For a second consecutive quarter, the Dallas-based airline posted losses--this time $56 million, or 8 cents per share--according to the Denver Business Journal , which notes that the airline saw $111 million in gains just one year ago. The reason for the struggle is the airline's bad betting on fuel prices, a problem that has also struck DIA's largest carrier, United Airlines. Earlier this week, United announced a $1.3 billion loss for the fourth quarter, adding 1,000 workers to its rising number of layoffs, according to The Associated Press . It is unclear how the layoffs will play out in Denver. While United expects reduced demand, officials for AeroMexico are hopeful a new flight between Denver and Mexico City, which starts February 1, will draw customers, according to The Denver Post .