[2] Founded in 1976, the carrier began service on most of the routes abandoned by Sun Valley Key Airlines.

[3] From its hub at Salt Lake City, the carrier served the following destinations at various times during its existence:[4][5] Transwestern also flew from Denver to Santa Fe and Albuquerque, New Mexico in 1977 and 1978.

[6] The Transwestern Airlines fleet consisted of the following aircraft:[7] A non-fatality accident in Idaho occurred on its route on February 15, 1983, on a late morning flight from Boise to Sun Valley.

On approach, the sub-contracted Sierra Pacific Airlines de Havilland Twin Otter pitched forward and an emergency landing was attempted on Highway 75, 1.7 miles (2.7 km) south of runway 31 of Friedman Memorial Airport in Hailey.

[8] The control rod connection had separated; poor maintenance procedure using a non-standard bolt was cited as the cause.