Sioux City Journal: SkyWest Airlines flight 5146, the first direct flight from Denver to Sioux City in six years, arrived at the Sioux Gateway Airport at 4:47 p.m. Wednesday. Sioux Gateway had been without flights to and from Denver since October 2014, when low-cost carrier Frontier Airlines halted the service after just four months. In the 1990s, United Airlines offered daily connecting flights to Denver. The city's transportation services agreement with SkyWest, which is flying United Express-branded flights, runs until Feb. 28, 2022.