SkyTeam member Alitalia has Philadelphia to Rome at $488 and New York JFK to Frankfurt at $524. Oneworld and Star Alliance do not come anywhere close to those fares. Star Alliance member TAP Portugal fares from New York and Newark are in low $500s, but there are very high bag fees associated with TAP Portugal flights. The other alliances are over $1,000 for Philadelphia to Rome.
PHL-Rome: $489 January 8 – April 6; $529 April 7 – May 11.
JFK – Frankfurt: $524 Jan 10 – March 31
Alitalia New York JFK – Rome FCO – Frankfurt FRA – Rome FCO – New York JFK
Alitalia Philadelphia PHL – New York JFK – Rome FCO – New York JFK – Philadelphia PHL