I was told by a Delta Airline agent that my flight from the states to San Juan was considered an international flight. Is this correct?

I'm not sure why it would be unless you are flying over international waters.

If you are flying from a U.S. airport to SJU, it is a domestic flight. However, it is taxed as an international flight and Delta applies other rules to these flights as though they were "real" international flights. Bottom line - you are paying more in extra fees and taxes than you would for a flight classified as domestic.

I guess a flight to SJU also invokes any international flight benefits one gets with their Skymiles account.

I had a similar issue with American about flying to Hawaii. I was told that I could use my "points" but it would be an international flight, thus additional points required. No good answer when I reminded them it was the 50th state. Go Figure.

Gee, I didn't know San Juan was one of the 51 States...that would consider it to be a Domestic Flight.