Well that's surprising. Is there enough gate space though? DL has a lot of flights out of PHX and B6 and Spirit are there too.
Also, according to Wikipedia it's even more routes:
Chicago-O'Hare (begins October 26, 2014),[21] Cincinnati (begin October 28, 2014),[22] Cleveland, Denver, Houston-Intercontinental(begins November 20, 2014)[23], Salt Lake City (begins November 20, 2014)[24], San Francisco (begins November 20, 2014)[25]