| Cheap Flights: San Antonio to/from Philadelphia $138-$167 r/t [August-January] â United United has round-trip flights from San Antonio (SAT) to Philadelphia (PHL) for $135-$167 with a connection. Flights August to January. Extended weekends available. Origin/Destination reversible. Note: Most flights are about $167, but Iâve listed all the $135 fares at the top of the list in this post. Click for more details and booking links Cheap Flights: San Antonio to/from Philadelphia $138-$167 r/t [August-January] â United . | 