I see your point, but it won't wash legally. The fact is that those fares are just not for sale. And they can't be forced to sell a service they offer. Suppose it was the cheapest fare class... you wouldn't dispute it not being available. We've all experienced fare classes opening and closing for no apparent reason (BA's whim
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If they wanted to, they could sell it under the rules, but they chose not to.. and that is that. Buckets bear no relationship to seat numbers, other than the fact that as long as one bucket is open, there is at least one seat available.