UA memo to agents:
"Other airline rebooking policy
Our irregular operations policy for rebooking on other airlines (OA) provides flexibility when there are no options on United. Settlement rates vary between OA carriers and preference should be given to rebooking first on United, then Joint Venture (JV), followed by other Star Alliance carriers before considering other interline airlines.
Although our OA rebooking policy has not changed, Delta (DL) should only be considered when all other options have been exhausted as our settlement rate with DL is significantly higher than with most carriers.
As a reminder:
OA may be used if the United rebooking option is not acceptable to the customer and does not get the customer to their final destination within four hours of their originally scheduled arrival.
Always offer options on United first, followed in order of preference by JV partners, then other Star Alliance carriers. Use DL only as a last resort.
Make every attempt to book long-haul portions on United and consider using a United connection before offering a non-stop flight on an OA.
Avoid rebooking on DL and other interline airlines, as their settlement rates are higher."