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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 100,469
If OP purchased tickets yesterday, they can still be cancelled for free. So call DL and ask about other flights with various connections where upgrade space can be confirmed and then change--technically cancel and purchase--the ticket to one where the SWU can be used now.
Note that SWUs expire one year after they are selected, meaning that they should be applied to a flight with confirmed upgrade space and the ticket reissued by then; travel can be latere.