Originally Posted by emma dog

OP is trying to get flight credits and not get a refund back to Amex.

OP: I'm guessing you mention 24 hours because you want to get full credit for your flights and not pay a change fee. All that is from pre-COVID days. Currently the entire ticket value for any flight other than Basic Economy can be applied to a future flight.

Buy any non-refundable ticket that meets minimum spend. I'd select something a couple months out just so you don't have to "stay on top of things." Wait >2 calendar days and then cancel the flight. It will become flight credits. You don't need to call DL... do it all online.