Originally Posted by
mnbp
As with many things DL, exactly which fares qualify for Amex cert use is opaque.
However, there is one thing certain - broken fares (more than one fare in each direction) won't work with the Amex cert.
Not IME. In fact for the trip where I used mine coming up, we're in different cabins. SEA-ATL and DTW-SEA in FC. ATL-RDU and RDU-DTW in Economy. ATL-RDU and RDU-DTW are both operated by aircraft with FC so no idea why it booked that way but since it was the short hops I'm not too terribly concerned.