Families of the 67 people who died in the midair collision between an American Airlines regional jet and an Army helicopter over Washington, D.C., in January sat front and center at a congressional hearing Thursday, calling for accountability and change in aviation safety. 

Tim Lilley, the father of 28-year-old Sam Lilley, who was serving as the first officer on American Airlines Flight 5342, expressed frustration at the preventable nature of the tragedy and that the necessary changes had not yet been implemented.