thefareguru suggested to fly from IAD* via VIE to THR on OS to avoid the second international departure from Germany. The legal routing would be:

ham-muc-hkg-bkk-sin-hkg-nrt-icn-nrt-hnl-sfo-mex-mty-mex-iad-chs-iad-vie-thr-fra-ham (= 33.650 miles)

But there are two more facts we have to consider (I do not know if they are relevant for sunseeker):

• OS does not offer a First Class cabin (IAD-VIE-THR would be D)
• On Mondays & Tuesday OS does not service VIE-THR

*OS has a non stop service out of IAD, therefore it is not necessary to fly IAD-JFK on UA in coach class.