In late January, a commercial American Airlines plane collided with a Black Hawk helicopter near Ronald Reagan National Airport during a training exercise, killing all 64 passengers and 3 helicopter crew members. Both aircraft crashed into the Potomac River.

Investigators found the helicopter crew had inconsistent altitude readings, with one pilot believing they were at 400 feet and the other at 300 feet. It’s unclear at what exact altitude the collision occurred. The NTSB noted possible bad data and radio transmission issues, where the helicopter crew may have missed air traffic control instructions.

Moments before impact, the helicopter pilots opted to use visual flight rules to avoid other traffic—a common but riskier practice. Communication errors, including overlapping radio transmissions (“stepping on” instructions), also contributed to the crash.

Additionally, tracking technology on the Black Hawk was turned off, as would be typical during a real mission. Brig. Gen. Matthew Braman stated that multiple factors combined to cause the tragedy, any one of which, if changed, might have averted disaster.