I could see the A321XLR in a role in DL's fleet, but realize in a config with lie-flat J seats it would likely hold about 160-165 pax max. The next step up will be the A330-200 at 234 pax. That is a significant gap, but not unmanageable. Given DL's previous decisions to purchase/lease used aircraft I could see DL picking up some more A330-200s. I think the capital costs of new A330-800s does not make sense.