Actually, after reading the letter, I thought their concern was the wording prohibiting "...their constitutional right to the judicial system." against "... air carriers and their allies."

I think the concern is about the clause trying to prevent lawsuits against the various participants and supporters of this piece of legislation. I believe that would include those with a seat at the table.

I'm certainly not an expert - but I bet that if some of the lawyers in congress/senate actually had read the resolution, they would not have voted for it. "What do you mean they can't sue someone!!! By gosh, that's their God-given right!!! This is America"