Check out the Alaska Airlines website. Alaska serves PHL.
Earlier this year, I needed to go to Maui for business. Delta LUT coach was $1,500.00 and their cheapest discounted premium fare was north of $2,500.00; Alaska had a full F fare at $1,900.00. I did get 200% MQMs from Delta for this.
Therefore, if you need an F fare to go someplace out west, make sure you check Alaska's site.