I think you did not read all of my reply. Without going into great depth, I am very familiar with yield management, hence my note (in parentheses) last time giving the caveat that changes should be allowed (at a fee) as long as seats are still available in that fare bucket.

This is standard on any fare on any airline (AFAIK)... if the seat is not available in that bucket, then you can't change to that flight without upgrading to the next fare class.

In other words, the person who paid full fare J will not have someone next to them who paid the discount fare.... unless yield management decides that they can't sell all seats at full fare and opens a few seats up in the discount bucket.....but if they don't allow ANY changes, then that changes the yield management picture, as many people would not buy the discount tickets if they are point blank not changeable.

Oh, and how many people really pay full fare J on BA... their transatlantic routes are chock full of people in J / F paying negotiated corporate rates at much less than the public fare, not to mention the complimentary BAEC Gold Cards that all those corporate staff get thrown at them

Anyway, this conversation is getting way too esoteric and on topic (god forbid) for me... so I will close now !