Excerpt from UA Rule 240 (pages 33-38, United COC)

9) SCHEDULE CHANGE MEANS:
A) THE CANCELLATION OF A SCHEDULED FLIGHT WHERE NO UA FLIGHT OF COMPARABLE ROUTING IS AVAILABLE WITHIN 90 MINUTES HOURS OF THE ORIGINAL TIME OF DEPARTURE;
B) A CHANGE IN THE SCHEDULED DEPARTURE TIME OF A UA FLIGHT WHICH EXCEEDS 90 MINUTES;
C) A CHANGE IN THE ROUTING OF A SCHEDULED UA FLIGHT WHICH ADDS ONE OR MORE STOPS TO THE ORIGINAL ITINERARY; OR
D) A CHANGE IN THE ROUTING OF A SCHEDULED FLIGHT THAT RESULTS IN A SCHEDULED ARRIVAL TIME MORE THAN 90 MINUTES LATER THAN THE ORIGINAL SCHEDULED ARRIVAL TIME.

D) SCHEDULE CHANGES
IN THE EVENT OF A SCHEDULE CHANGE OF A UA FLIGHT ON WHICH A PASSENGER HOLDS A TICKET INDICATING A CONFIRMED RESERVATION, UA WILL:
1) OFFER TO TRANSPORT THE PASSENGER OVER ITS OWN LINES IN THE SAME CABIN AS THE PASSENGER WAS ORIGINALLY SCHEDULED TO TRAVEL TO THE DESTINATION, THE NEXT STOPOVER POINT LISTED ON THE TICKET, OR THE TRANSFER POINT SHOWN ON ITS PORTION OF THE TICKET WITHOUT
STOPOVER, AT NO ADDITIONAL COST TO THE PASSENGER, OR
2) AT UNITED’S DISCRETION, ARRANGE FOR THE TRANSPORTATION ON ANOTHER CARRIER OR COMBINATION OF CARRIERS WITH WHOM UA HAS AGREEMENTS FOR SUCH TRANSPORTATION; THE PASSENGER WILL BE TRANSPORTED WITHOUT STOPOVER ON ITS (THEIR) NEXT FLIGHT(S), IN THE SAME CLASS OF SERVICE AS THE PASSENGER’S ORIGINAL OUTBOUND FLIGHT AT NO ADDITIONAL COST TO THE PASSENGER; OR
3) IN THE EVENT THE PASSENGER DECLINES ALTERNATE TRANSPORTATION OFFERED UNDER (1) OR (2) ABOVE, REFUND IN ACCORDANCE WITH RULE 260 (REFUNDS-INVOLUNTARY).
E) IN THE EVENT THAT UA CHANGES THE TIME OF DEPARTURE OR ROUTING OF A FLIGHT IN A MANNER THAT DOES NOT CONSTITUTE A SCHEDULE CHANGE AS DEFINED HEREIN, WHETHER OR NOT THE SAME FLIGHT NUMBER IS RETAINED, UA WILL TRANSPORT THE PASSENGER ON THE RESCHEDULED FLIGHT AT NO ADDITIONAL COST TO THE PASSENGER.