On April 4, 1991, Pennsylvania Senator H. John Heinz III was killed when his airplane collided with a Sun Company helicopter in what is known as the Merion air disaster. Falling debris killed 2 children at the Merion Elementary School in the Lower Merion School District. The National Transportation Safety Board determined that the probable cause of the accident included poor judgment on the part of the captain of the Sun Company helicopter, and his failure to maintain safe separation from the Senator's airplane.