In November 1997, Mesa negotiated a codeshare agreement to provide service to US Airways as US Airways Express for 14 regional jets to various cities from its Philadelphia and Charlotte hubs. In 1998 and 2000, the agreement was expanded to 28 jets and then to 52 jets. The first CRJ200 aircraft began operating in 1998. As Mesa began taking deliveries of the Embraer ERJ 145 aircraft in 2000, the CRJs were transferred to the America West division, separating the fleet types.