What is the relationship between American Airlines Group and US Airways in the context of the input sentence. Choose an answer from: 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 .
subsidiary