Philly plane crash: Just 30 seconds after takeoff, flight disappeared from radar. A look at likely causes of tragedy

Philadelphia plane crash: An air ambulance carrying a young girl, her mother and four crew members crashed into a busy residential area of northeast Philadelphia Friday, erupting in a fireball. It happened just two days after a deadly mid-air collision between a Black Hawk helicopter and an American Airlines passenger plane above Washington D.C. killed 67 people. There were no survivors.