Reservation Changes, Delta UGH
 

In April 2008 I made a reservation using Sky Miles for a flight on 1/29/09 LAX to Puerto Vallarta. On 1/14/09 I went on line to check in & found Delta had changed my itinerary without consulting me. The changes were totally unacceptable. They didn't even try to reschedule me to one of their Partner Carriers. Instead I was routed to Salt Lake City with an overnight delay, flying to PVR on the 30th. Then they cancelled my return flight & rescheduled me two days earlier. What a way to screw up a vacation. After much haggling with an agent I cancelled the ticket & have no idea what is going to happen to the monies & Sky Miles I used.
I went on line after that & was able to get a flight for the days & times I wanted. It took five minutes!
Delta, never again.

The earlier you make a reservation the more likely the times and routings are going to change. Airlines add/remove/change flights/frequencies/schedules all the time.

The reason you were initially re-scheduled via Salt Lake City is because you redeemed Delta Miles for a Delta award on Delta aircraft. In many cases partner award would have cost you more miles to begin with and they are not going to deduct more miles from your account nor are they going to "eat" the difference because Delta has to pay the partner for the space they reserve for you.

Regardless if you make a reservation with miles or dollars if a schedule change is significant you can get a refund of your money and/or re-deposit of yur miles with no fee.