The airport was built in 1942 as Flathead County Airport, from which its IATA and original FAA and ICAO codes were derived. Airline flights operated by Northwest Airlines began in 1950; however, passenger traffic was sparse for years. In 1970 the airport was designated as an international airport and received its current name. In the 1970s and 1980s passenger traffic increased as Hughes Airwest (previously Air West), Western Airlines, Delta Air Lines (which acquired Western), the original Frontier Airlines (1950–1986) and Horizon Air offered new jet service. Jetliners operated into the airport in the past include the Boeing 727-200, Boeing 737-200, Boeing 757-200, McDonnell Douglas DC-9-30 and Fokker F28. The 757 operated by Delta is the largest aircraft ever to have provided scheduled passenger service at the airport. The terminal was upgraded in 1981, and further upgrades to the terminal, runways and other facilities occurred in the 1990s. Between 1974 and 1998, passenger traffic increased more than fivefold. In 2018, planning efforts began to expand and modernize the terminal building in its existing location. After a delay due to the COVID-19 pandemic, construction began in spring of 2021. "Phase 1A" of the project (new hold rooms, security checkpoint, basement, and administration offices) opened in March 2024, Phase "1B" (renovated ticketing lobby, central atrium, and renovated baggage claim) opened in May 2025, and "Phase 2" (three additional hold rooms and a third bag claim device) is scheduled to open in spring of 2026. When complete, the terminal building will be approximately 200,000 square feet (up from 75,000 before the project). Total project costs are estimated to finish at approximately $165,000,000. Service to Phoenix, Arizona, on US Airways (formerly America West Airlines before it merged with US Airways) ended in 2007. West Coast Airlines served the airport in the 1960s with Fairchild F-27 turboprops flying to Spokane, Seattle and Great Falls before this carrier merged with Bonanza Airlines and Pacific Air Lines to form Air West, which continued F-27 service from Kalispell. Air West was then renamed Hughes Airwest which in turn introduced McDonnell Douglas DC-9-30 jet service. The original Frontier Airlines operated Boeing 737-200s during the 1970s with a routing of Kalispell–Missoula–Bozeman–Salt Lake City–Denver–St. Louis. By the 1980s, Frontier was continuing to operate Boeing 737-200s with Kalispell–Billings–Denver flights. Cascade Airways operated Fairchild Swearingen Metroliners (Metro III model) into FCA until it folded in 1986. In the 1990s, Horizon Air, a subsidiary of Alaska Airlines, flew Fokker F28 jets to Spokane and Seattle in addition to operating propjet service with de Havilland Canada DHC-8 Dash 8s, Dornier 328s and Fairchild Swearingen Metroliners. Current Alaska Airlines service into the airport is operated by Horizon Air with the Embraer 175 regional jet.