It was the result of the TWA fiasco, but 7 years too late.

Previously, if a carrier acquired another carrier who had the same union, then the union process would determine seniority (ie AAA/AWA). This may be a contentious process, but nobody is going to get boned, or at least everyone gets boned equally. I know the AAA guys THINK they got the raw end, but that actually got a better deal seniority-wise than AWA. The problem there is that the AAA guys are so old that most will retire in the next 5-10 years and not have much time to benefit from their seniority.

However, if a carrier acquired somebody with a different union (or no union), there were no rules, the acquiring carrier could do whatever they wanted: Fair integration, staple, or just fire all of the acquired pilots. Effectively AA stapled and then "furloughed" all the TWA pilots (and FA's). Few will ever return.

The McCaskill bill prevents this sort of behavior going forward...it requires by law that acquired or merged pilot groups get integrated fairly (using a seniority formula). I think that if both groups are the same union, then internal union rules prevail, otherwise a certain formula is required (Alleghany-Mohawk).

The significange to this is that non-union SKW cannot be stapled by alpa, even if SKW management decided to allow that for some reason. It would also protect ASA/XJT from being stapled by SKW. The law clearly applies in the event of actual merger. I'm not sure how it applies to a holding company which operates multiple certificates...it may not protect against moving airplanes around. The courts would probably have to decide that.