SDC between co-terminals is technically not allowed. (Which isn't to say that it can't be done).
SDC between "Multi-airport cities" IS allowed, but there's only 2 pairs of them that UA fly to - JFK/LGA and IAD/DCA.
I've had no problems changing flights between multi-airport cities in the past (most recently just over a week ago), but I've failed on two of the three occasions I've tried to do it with EWR being involved - with the one time I succeeded being during IRROPS.
Originally Posted by
garykung
2. Even SDC within the same city pair possible, SFO-JFK is p.s. Agents tend not to allow such change (And again - personal experience, SJC-DEN-LGA to SFO-JFK).
This one is definitely allowed. I've had GA's deny it in the past as p.s. is a "different class of service", but in the end I've always succeeded after a bit of pushing.