Concur with second poster that DTW-RDU/STL look to be the cheapest at $111 roundtrip. I would not involve another airline (particularly Spirit) for positioning as you won't be protected on return in the case of irregular operations. DTW-AUS can be had for $131 sameday roundtrip on a number of Tue. and Wed. dates in December and will goose your rollover a bit (earns around 2300 MQM's total).
Last edited by xliioper; Nov 16, 2019 at 11:19 am