Doubt the Airlines could win, they broke several of their own policies, United doesn't have a leg to stand on. That is why the CEO finally after several statements, issued a "true" apology and admitted the customer was NOT at fault. The CEO didn't back track his initial statements of backing the companies policies and of the employees because he felt it was the right thing to do. I guarantee he backtracked due to advice from their own legal counsel. They know it isn't winnable and want to try to settle as soon as possible. It also doesn't help their case when the Aviation Security Office in Chicago also stated that the incident was not within standard operating procedures and will not be tolerated.
It's a longshot, but Demetrio may be considering a class action lawsuit against Airlines business practices. There are no shortage of airline horror stories or suspect business practices. He was happy about the slam dunk case, but that big smile you saw was him dreaming of a huggggge class action lawsuit against the airlines. He may not pursue that, but you gotta know he's thinking about it.