The remaining J seats are already sold via ~$299 upsell offers on the app. That is more damaging to GUC value than this announcement.

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I've never bought a basic economy ticket in my life, so I have trouble keeping up with what the 3 stooges (DL/AA/UA) are doing vis a vis included perks. AA does let me select a seat, even MCE seats, with my status on a BE ticket. That's appealing. Until DL monetizes the J cabin seatmap for this rollout, we won't really know. On a clapped-out 767, there's zero chance I'd pay for a seat assignment in J, because they're all terrible. On an A350, I might be willing to pay for an air nozzle (cough, I mean window). I can solve the lounge problem by booking from a gateway that has a Centurion lounge, and Priority Pass lounges are plentiful in Europe and Asia. I never check bags. If these fares migrate across JV metal, and I can't get a seat assignment, I'd probably just book the option with the best metal / hard product and call it good.