Southwest Airlines on March 7 will begin daily nonstop flights between Des Moines and Denver. Departures from Des Moines will be at 3:20 p.m. with return flights landing in Des Moines at 10:50 a.m. Southwest joins Frontier and United Airlines among carriers serving Denver from Des Moines. The Denver market is the third-largest destination for Des Moines travelers, averaging 185 passengers a day each way. Southwest’s other nonstop flights from Des Moines go to Las Vegas, Phoenix and St. Louis.