Posting for a friend:

Her daughter spent a semester abroad returning thru JFK prior to Xmas (post the snowstorm). She had a JFK-xxx-JFK roundtrip booked on BA, then a one way from JFK-home booked separately on Delta.

Due to weather in Europe her BA flight was delayed, and she missed her Delta flight home. Delta told her that couldn't get her home for 4 days; told her to "find another airline". Her father called his amex agent who was able to book a oneway on NW for the next morning ($700) and a hotel for her to overnight as they wanted to get her home for Xmas (not sure why the DL agent couldn't see this flight, but AMEX could).

Are they only owed a credit for the "unflown" portion, or should there be someway for them to recoup the $700? How should I advise them - is calling best, or is it better for a written letter?

The answer depends on the fare rules. Since this was booked as a separate ticket, the traveler's failure to check-in and present herself at the gate on time could mean she has forfeited the entire value. This is a risk one takes when using separate tickets with a second, highly restricted component.

To clarify a little on 3C's post, the $700 is gone, sorry. The only thing left in question is the value of the unused JFK->home ticket which will depend on it's fare class.

This is the danger on flying split tickets. DL has no responsibility for BA's late flight when on another ticket. If it was the same ticket things are different. From DLs point of view, you just did not show up for the flight.

I fly split tickets across the Pacific all the time. But I realize that sometime I will get "burned" by it.

If you want to plead for "symapthy points", I would try BA not DL.

The original DL ticket, if unused should represent a credit available for 1 year. There will be a change fee to re-issue it for a future date, and it can only be used in her name, but the entire amount is not lost assuming she will need to fly somewhere in the next 12 months on DL.

Retain the original record locator and ticket number for future reference and call an agent to confirm the credit. A refund however, is not going to happen unless on a fully refundable $$$$$$$ ticket.