Originally Posted by
jrl767
DL had (and may still have) a handful of through flights that operated with the same flight number on both segments; most involve(d) a domestic segment at the beginning or end of an international flight
some where I was on the domestic leg were DL151 IAD-ATL (M88; continued to LIM as a 763/764) and DL159 DTW-BOS (319; came in from ICN as a 744)
I also flew DL939 IAD-SLC-SEA, which was a tail swap of 738s (and despite several rounds of negotiations, did NOT get credit for the two segments on a wholly domestic flight

)
There are some domestic routes where the aircraft turns around, usually RJs, with the same flight segment. IIRC DTW-ITH-DTW is one example.