Well...it depends. If I get the American based agents for Delta they are more than willing to make changes and I have made two so far to my returnportion (the outbound change incurs a fee and fare re-calculation). I called last night and spoke w/ an American based agent who noted my file that I WOULD be able to use another carrier in Europe as long as I take a Delta coded flight (DL or Codeshare) over the water. I also wrote to consumer affairs re: them not allowing changes and they so kindly noted my record to state that I could make changes as long as they fall within the fare rules.

When I have had the pleasure of speaking with the agents from India or the UK, they are unyielding and down right rude re: changes on this fare. So I say keep calling back until you get the answer you want. ^