Thanks for the quote, but I think you cherry picked. So let me do the same thing. Here's a quote from farther down the page. "The final regulations provide guidance on the circumstances under which a qualified retirement plan can be amended to eliminate or reduce early retirement benefits, retirement-type subsidies, or optional forms of benefits. Specifically, the final regulations provide rules under which a plan may be amended to eliminate benefits that are burdensome to the plan and participants and have minimal value to plan participants."

Yes I also picked a quote that really does not add to the discourse either. But that's what you did. Posting an answer you knew did not answer the question. In full disclosure, I cannot find any reference where an employee group amended their contract to reduce a benefit. But I also cannot find any reference that says an employee group is prohibited from decreasing their benefit. Ball is still in your court. Where does it say an employee group cannot decrease their own benefit??? That is the posed question. Could the A plan be contractually diminished down the road by the pilots?