Four people were injured Sunday afternoon when a USAirways flight hit severe turbulence shortly after taking off from PhiladelphiaInternational Airport, an airline spokesman said.Three people, including two flight attendants, were taken to hospitals for treatmentafter the plane returned to Philadelphia, CNN reported spokesman McGlashen assaying.There were 265 people on board, including a crew of 10, when the Airbus A330 hitturbulence at about 17,000 feet over Delaware.Flight 735 was flying from Philadelphia to Orlando at the time of the incident. Therehad been some reports of light turbulence in the area, but nothing as severe as whatthe plane ran into. The Federal Aviation Administration will investigate.In a separate incident, the wing of a WestJet 737 clipped the horizontal stabilizer of a JetBlue plane while on the ground at Orlando International Airport. The horizontalstabilizer is the back set of wings. The WestJet flight was pushing back from the gate when the incident happened,according to the FAA.