Our 738 to jfk died at the gate today. Replacement bird is here now. Of course I called the EXP line as soon as I got off the plane and asked the agent to protect me on the next flight in J. She did and confirmed me on a BA 744 <redacted> in J. Then she asked me "if you make AA 100 please call us back to cancel the BA flight".

I've never heard this before and was wondering why wouldn't AA know when and if I board my originally scheduled flight and subsequently cancel the BA ticket? Why is the onus on me?