US Airways Group Inc. is the Tempe, Arizona-based airline holding company that operates US Airways and US Airways Express; before the 2007 merging of operating certificates, the group also managed America West Airlines. It also operates additional companies that provide associated services. ACE Aviation Holdings, the Canadian parent of Air Canada retains a roughly 6.1% investment stake in the US Airways Group of airlines. When combined, the US Airways Group airlines form the largest low-cost, hub-and-spoke based airline network in the U.S.. The network covers destinations in 47 states, as well as numerous international destinations.