A daylong hearing on Tuesday should make clear what factors played the biggest role in causing last January’s midair collision near Washington, D.C., that killed 67 people. Everyone aboard an American Airlines jet flying from Wichita, Kansas, and an Army Black Hawk helicopter died when the two aircraft ran into each other and plummeted into the icy Potomac River. The Federal Aviation Administration made several changes soon after the crash to ensure that helicopters and planes no longer share the same crowded airspace around the nation’s capital, while the NTSB aims to recommend further actions. Rachel Feres, who lost family members in the crash, expressed hope for meaningful changes to prevent such tragedies from occurring in the future.