A FlyerTalk Posting Legend
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: 100,465
AS miles can be earned and redeemed on DL, AA, and of course AS, maybe others. This flexibility makes the AS program a good place to deposit miles that might otherwise be orphaned, especially for anyone who travels an DL and AA regularly, but not enough for elite status with either.
Most airlines now are offering not status matches but status challenges now, if at all, and the challenges tend to be restricted to those who are already elites on certain carriers. Exceptions seem to be offers to BMI participants and the infamous recent UA 1K to AA EXP.
I suspect that everyone's situation here is different, starting with whether one hopes to gain status on another carrier or simply a nice or useful award ticket from the trip.
If one wants IFC award tickets, note that SkyTeam does not permit this using miles of an airline that does not offer IFC. So putting miles into DL limits aspirational awards to their business class (BE), partner business class, or domestic FC. FB allows IFC awards, but only for their own top tier elites. Your best bet might be to consider how easy it would be to use KE miles for an IFC award ticket on KE, which has extensive blackout dates. Note that one way award tickets from DL miles cost the same number of miles as RT award tickets, which normally allow one stopover (at a legal connecting point) and one open jaw.