When a passenger jet roaring down the runway toward takeoff at New York's LaGuardia Airport had to slam on the brakes earlier this month because another plane was still on the runway, Renee Hoffer and all the other passengers were thrown forward in their seats. Hoffer wound up in the emergency room the next day after the near miss on May 6 because her neck started hurting and her left arm went numb. "The stop was as hard as any car accident I've been in," Hoffer said. Both the Federal Aviation Administration and the National Transportation Safety Board said Monday that they are investigating the incident in which a Republic Airways jet had to abort takeoff and slam to a stop because a United Airlines plane was still taxiing across the runway. The close call happened despite the airport being equipped with an advanced surface radar system that's designed to help prevent such close calls.