The biggest is Parker's history. He's never proposed a merger with another airline that was in bankruptcy and a merger was part of the POR.
Then there are factors that are beyond my limited knowledge. The current stockholders would have to approve the merger since the current stock doesn't get cancelled until a POR takes effect, possibly as well as the UCC. Has he been courting the current stockholders? No, only the UCC. What does he give the current stockholders for their AA stock? Money or LCC stock and the current AA shareholders could come out smelling like a rose compared to what awaits them if US just has a POR that includes a merger accepted by the UCC. Then, if merging with AA while it's in bankruptcy, US has to give the creditors something for their claims and can't treat them worse than the current AA stockholders. If the current stockholders get 100% of the value of their AA stock, the unsecured creditors can't get less than 100% of their claims paid. How about US - if it merges while AA is in bankruptcy that that mean the combined company is then in bankruptcy?
I'm sure there's some I can't think of...
So I don't think there's a snowballs chance in hell that a merger will happen except as part of an accepted POR, just as happened with US/AWA.
Jim