Find airlines with flights to Montrose Airport, MTJ. Airlines · Allegiant Airlines See information about Allegiant Airlines. The Montrose Regional Airport is proud to bring you the best in aviation services on the Western Slope of Colorado. Montrose Airport (IATA: MTJ, ICAO: KMTJ), also known as Montrose Regional Airport, is a small airport in United States with domestic flights only. Enter your preferred departure airport and travel dates into the search form above to unlock the latest Montrose flight deals.