PHL stands for Philadelphia Airport, while AVV stands for Melbourne Avalon Airport. These codes are often called IATA codes, a set of identifiers established by IATA (International Air Transport Association) that is widely used by airlines and the aviation industry. Pittsburgh Airport (PIT), Harrisburg Airport (MDT), Allentown-Bethlehem Airport (ABE), Wilkes-Barre Scranton Airport (AVP), State College University Park Airport (SCE) are some additional IATA codes for airports related to your trip.