Beware of using multi-city search with Matrix as it doesn't correctly check married segment inventory when attempting to combine segments on a single fare (if the connection is an allowed routing for a fare and connection time is below layover maximum for the fare). Basically, it quotes fares based on individual bucket inventory, which may or may not match the married segment inventory. Married segment inventory needs to be used when combining segments on one fare. You won't know if it quoted a valid fare until you get to the final checkout payment on delta.com as it only does a check on married segment inventory at that point. One-way and roundtrip searches are fine and you can generally get these to give you the itin you want by playing with preferred times and such.