On February 24, 2011, about 1700 eastern daylight time, US Airways flight 1556, an Airbus A321-211, N162UW, encountered turbulence during arrival into Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. Of the 189 passengers and crew onboard one passenger received serious injuries and the airplane was not damaged. The flight was operating under Title 14 CFR Part 121 as a regularly scheduled domestic passenger flight from Fort Lauderdale–Hollywood International Airport (FLL), Fort Lauderdale, Florida. The first officer was the pilot flying and the captain was the pilot monitoring. The flight crew stated that they were in instrument meteorological conditions and level at 13,000 feet and 250 knots when they encountered severe turbulence and two separate lightning strikes. The flight crew stated that the weather radar was on and displaying only green returns. The crew indicated that the seat belt sign was on, and had been on since passing through 18,000 feet. They indicated that turbulence lasted about 10-15 seconds and the airplane immediately lose 20 knots airspeed and pitched violently in all three axes. In addition, the airplane lost about 150 feet in altitude and the autopilot disengaged. While the captain was reporting the severe turbulence to Air Traffic Control, the flight crew was notified by the flight attendants that a passenger was on the floor and was apparently injured. When the turbulence was encountered, a passenger was exiting the mid-lavatory and sustained serious injuries. The A flight attendant stated that as she had been in the back of the airplane and that they encountered the turbulence when she was walking back to the front. She said that she did not see the passenger actually fall, but after the turbulence, saw the passenger lying on the floor outside the 3L lavatory. The flight attendant said she immediately dropped to the floor since to assist the passenger and had two men in the exit aisle seats put their arms around her to secure her in case the airplane encountered additional turbulence. The flight attendant said she then told a flight attendant seated in the aft galley to inform the captain of the event.