The pilot of US Airways Flight 4321 from Elmira Corning Airport [ELM] Airport reported sighting a flare off the right wing of the regional jet while on approach to Philadelphia International Airport (PHL) last Tuesday and said the flare came within 50 feet of the aircraft. The airplane landed safely on Runway 17 and the FAA notified law enforcement officials. Police searched near PHL after the incident, but were unable to locate evidence of the flare.