Utilize the input text as a context reference, choose the right relationship between US Airways and American Airlines Group from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Shares of United over the past five years have generated about half the return of rival Delta Air Lines , and analysts have worried the company is falling behind once-bankrupt American Airlines Group as that company integrates its merger with US Airways Group .

Answer: parent_organization