AA INX1C1S4 fares appear to allow three transfers within the US (two AA domestic segments, plus an additional one on Alaska), but I've had no successes on Matrix so far. Did I miss something?
Category 9: Transfer restrictions
2 TRANSFERS PERMITTED IN EACH DIRECTION FREE
1 PERMITTED FREE BETWEEN AA AND VY IN BCN/ROM IN EACH
DIRECTION
NONE PERMITTED FREE BETWEEN AA AND VY IN EACH
DIRECTION
2 PERMITTED FREE ON AA/AY/BA/IB ONLY IN EUROPE IN EACH
DIRECTION
1 PERMITTED FREE BETWEEN AA AND ANY OTHER CARRIER IN
EUROPE IN EACH DIRECTION
1 PERMITTED FREE BETWEEN ANY OTHER CARRIER AND AA IN
EUROPE IN EACH DIRECTION.
AND - 1 TRANSFER PERMITTED IN EACH DIRECTION FREE
INTERLINE INCLUDING THE PRIMARY CARRIER
1 FREE BETWEEN AA AND HA IN HNL IN EACH
DIRECTION
1 FREE BETWEEN AA AND 9K IN STL IN EACH
DIRECTION
1 FREE BETWEEN AA AND AS IN LAX/SEA/SFO IN EACH
DIRECTION
1 FREE BETWEEN AA AND B6 IN BOS/EWR/JFK/LGA IN
EACH DIRECTION.
AND - 2 TRANSFERS PERMITTED IN EACH DIRECTION FREE
ONLINE ON THE PRIMARY CARRIER
2 FREE ON AA ONLY IN NORTH AMERICA IN EACH
DIRECTION
FARE BREAK SURFACE SECTORS NOT PERMITTED AND
EMBEDDED SURFACE SECTORS PERMITTED ON THE FARE
COMPONENT.