Mesa Airlines, Inc., is an American regional airline based in Phoenix, Arizona. It is an FAA Part 121–certificated air carrier operating under air carrier certificate number MASA036A issued on June 29, 1979. It is a subsidiary of Mesa Air Group and operates flights as United Express via respective code sharing agreements with United Airlines. It serves more than 180 markets in the Western Hemisphere. In a 1997 article from the Journal of Air Transportation, Mesa's safety record was noted as having the fewest incidents among domestic regional airlines at that time. Mesa filed for Chapter 11 bankruptcy in January 2010, hoping to shed financial obligations for leases on airplanes it no longer needed and emerged from bankruptcy in March 2011. In November 2017, Mesa opened a new training center in Phoenix. The 23,000-square-foot facility features a full-size CRJ-200 cabin trainer aircraft, 14 classrooms, and has the capacity to train 300 crew members at one time.

The Bombardier CRJ550, CRJ700, CRJ705, CRJ900, and CRJ1000 are a family of regional jet airliners that were designed and manufactured by Canadian transportation conglomerate Bombardier between 1999 and 2020. Their design was derived from the smaller CRJ100 and 200 airliners, the other members of the Bombardier CRJ aircraft family. The CRJ program was acquired by the Japanese corporation Mitsubishi Heavy Industries in 2020, which ended production of the aircraft.