“In the US Airways – America West case, it went to binding arbitration but there was a requirement as part of that that the two unions negotiate a joint contract with the company, which wasn’t done yet.
“And because it wasn’t done yet, the side that didn’t like it could prevent a joint contract from getting done. And because of that, the seniority integration never happened."
J. Scott Kirby
http://aviationblog.dallasnews.com/2012/05/kirby-we-expect-an-amr-us-airw.html/