Originally Posted by
MSPeconomist
In principle, with DL miles you can book any available seat on DL at HIGH miles (of low/medium/high), but there have been reports of even high miles not always giving last seat availability.
Also with DL miles, if you have a DL AmEx card, you can use pay with miles for any fraction you wish of a ticket purchased through DL at approximately one cent per mile.
My understanding is that UA's "standard" award (HIGH miles) availability does not mean "last seat" unless you have a United credit card or United elite status.
I don't know whether DL has any similar "unlock" of extra inventory that comes with some or all status.
AA has "unlock" of extra "saver" inventory sometimes for its top level of status (EXP), but that's different. At AA "anytime" awards
do give anyone (even without status/card) the last seat,
unless the cabin is being "oversold" in which case
no one can as an "anytime" award to get the last seat that can be bought.
(And so that's yet another question about DL exceptions, were they oversold flights or something more than that?)