How can i find routing allowances for a D fare SDC
I have a D fare PEK-SFO. I want to fly the night before and there are flights that go PEK-ORD-SFO, PEK-EWR-SFO or PEK-IAD-SFO. Is there a way to find out if those are legal routings? the ticket was pricey, so i'm guessing the routing rules are fairly liberal. but i'm guessing the app won't offer the options. and if i call, none of the routes seem natural so an agent likely will question it. but if there's a way to know the rule that would be awesome.
i know for instance, AA cheap coach fares allow routing PEK-ORD-LAX/SFO or PEK-DFW-LAX/SFO as i've bought these tickets many many times. but since they have no other connection points, they may not have a choice in routing rules. UA may be different.
thx in advance.