Originally Posted by SuperEWR

The "basic math" doesn't pencil out. Air France flies an A350-900, same plane as Delta's A350-900, with Safran Optima seats, the same seat as United's Polaris. Air France fits 34 Optima seats in between doors 1 and 2 along with half a galley, while Delta manages to fit 32 seats in between doors 1 and 2 with no galley and the center row 9 seats going into the space between doors 2. You can definitely cram in 1 more row of Optima seats and match the amount of space that D1 is taking up, maybe even cram in a second row in the center, so that would result in 38-40 Optima seats taking up the same space as 32 D1 seats, or 19-25% more seats vs D1. If the difference in the number of J seats is due solely to density, a 40J "high-J" (for a handful of the most premium routes) D1 cabin implies a 48-50 seat Polaris cabin for premium routes on an A350-900 sized plane. Does that match up with how UA has configured the planes that it uses for premium routes (let alone the most premium)? Not at all. I would argue that the 787-9, 777-200 and 777-300ER are most comparable to the regular 32J D1 as UA flies a large fleet of each of those aircraft on a variety of (mostly premium long-haul) routes, while the high-J 767 is a a small sub-fleet serving the specific purpose of putting in more J capacity for a handful of routes with outsized premium demand, while the new high-J A350 is (at least from indications so far) a small sub-fleet serving the specific purpose of making the South African extra-long routes feasible by cutting down passenger count.