US Airways Group Inc. was an airline holding company based in Tempe, Arizona. US Airways Group operated US Airways, along with its subsidiaries PSA Airlines, Inc. and Piedmont Airlines, Inc., which are wholly owned but marketed under the branding of US Airways Express. It merged with America West Holdings Corporation, parent of America West Airlines, in 2005, and the combined company adopted the better-known US Airways name; the two airlines' operating certificates merged in 2007. It also operates additional companies that provide associated services. ACE Aviation Holdings, the Canadian parent of Air Canada retained a roughly 6.1% investment stake in US Airways Group. The route network covered destinations in 47 states, as well as international destinations.