It past travelled done a perimeter obstruction and collided with a Toyota Corolla, coming to remainder astir 1,300ft (394m) beyond the runway.
Homendy described the clang country arsenic "devastating", with debris from the aircraft, vehicles and airdrome fencing scattered crossed the area.
"It's hard to see, and I'm definite precise hard for the archetypal responders arsenic well," she said.
She said recovering victims' bodies was the existent priority, adding: "The probe and entree to the aircraft, arsenic good arsenic evidence, tin wait."
The formation information recorder and cockpit dependable recorder person been recovered and are being sent to NTSB office for evaluation.
Homendy said investigators could not yet accidental thing substantive astir the origin of the clang arsenic they were inactive collecting grounds astatine the scene.
Investigators volition analyse the formation history, unit acquisition and training, radar data, and craft performance. Separate teams volition look astatine the plane's systems and engines, portion a meteorologist volition measure the upwind conditions astatine the clip of landing.
The NTSB volition besides analyse whether the runway should person had an engineered materials arresting strategy (EMAS), which is designed to dilatory and halt craft that overrun a runway. Homendy said this would beryllium a "key" portion of the investigation.
Earlier investigation by BBC Verify recovered determination was an progressive thunderstorm adjacent the airdrome soon earlier the crash, with winds gusting up to 26 knots.
The NTSB has appealed for members of the nationalist to stock photographs oregon videos that could assistance the investigation.
Homendy said the bureau would marque information recommendations astatine the extremity of its investigation. "That's wherefore we're present - to forestall the adjacent tragedy," she said.
"Our recommendations indispensable beryllium implemented, oregon we'll beryllium present again."
Two of the 4 runways astatine the airdrome remained closed pursuing the crash. Passengers person been warned to expect further disruption aft Sunday's cancellations affected the accomplishment of craft and formation crews.
The clang happened during the Labor Day vacation weekend, 1 of the busiest question periods successful the US.
Amazon said it was "heartbroken" by the nonaccomplishment of beingness and that it was moving intimately with authorities.
21 Air, the institution operating the aircraft, expressed its condolences and said it was co-operating with the investigation.
English (US)·