A daylong hearing is underway that should make clear what caused a midair aircraft collision that killed 67 people near Washington, D.C. The National Transportation Safety Board will recommend steps to prevent similar tragedies. An American Airlines jet flying from Kansas and an Army Black Hawk helicopter collided and plummeted into the Potomac River a year ago. The Federal Aviation Administration has taken steps to ensure helicopters and planes no longer share the same crowded airspace around the nation’s capital. A NTSB investigator says air traffic control had a big workload around the time of the crash.

So many things went wrong last Jan. 29 to contribute to the collision between an airliner and a U.S. Army helicopter that killed 67 people that the National Transportation Safety Board isn’t likely to identify a single cause at its hearing. Instead, the investigators on Tuesday will detail all the things they found that played a role in the crash near Washington, D.C., and the board will recommend changes that should be made to help prevent a similar event from happening again. Family members of the victims hope those suggestions won’t be ignored the same way many past NTSB recommendations have been after other crashes.