I've negotiated plenty of mergers and acquisitions. This isn't a typical tender offer where the acquirerer offers boatloads of cash and stock in an attempt to take over a company; AA is in bankruptcy and thus, the unsecured creditors committee will want to see the numbers before they approve a merger with US.I've been involved in due diligence efforts. The one doing the buying doesn't need to show the one being bought their internal numbers.
AA is currently investigating potential mergers with several airlines, including US. Parker could rebuff AA (and refuse to open the books) but if he does, the Unsecured Creditors Committee will likely not vote to move forward with a merger with US. Imagine how that reads when Horton reports to the UCC that US refused to open the books and exchange confidential info. That will be the end of the road for US.