Two years I used US miles for a Business Class award ticket PHL-IAD-EZE on UA metal with US stock. The PHL-IAD UAX flight was canceled and there was no way to get me to IAD that day to catch my international connection to EZE. UA 1K reservation phone agent and ticket agent at PHL could/would not help me (no UA flight available / they could/would not re-route me to another carrier). I called US they were able to re-route me PHL-JFK on DL and JFK-EZE on AA. Both legs were booked in full revenue fares and got the miles on AA and DL programs with COS and full fare bonus.