It then travelled through a perimeter fence and collided with a Toyota Corolla, coming to rest about 1,300ft (394m) beyond the runway.
Homendy described the crash scene as “devastating”, with debris from the aircraft, vehicles and airport fencing scattered across the area.
“It’s hard to see, and I’m sure very difficult for the first responders as well,” she said.
She said recovering victims’ bodies was the current priority, adding: “The investigation and access to the aircraft, as well as evidence, can wait.”
The flight data recorder and cockpit voice recorder have been recovered and are being sent to NTSB headquarters for evaluation.
Homendy said investigators could not yet say anything substantive about the cause of the crash as they were still collecting evidence at the scene.
Investigators will examine the flight history, crew experience and training, radar data, and aircraft performance. Separate teams will look at the plane’s systems and engines, while a meteorologist will assess the weather conditions at the time of landing.
The NTSB will also examine whether the runway should have had an engineered materials arresting system (EMAS), which is designed to slow and stop aircraft that overrun a runway. Homendy said this would be a “key” part of the investigation.
Earlier analysis by BBC Verify found there was an active thunderstorm near the airport shortly before the crash, with winds gusting up to 26 knots.
The NTSB has appealed for members of the public to share photographs or videos that could aid the investigation.
Homendy said the agency would make safety recommendations at the end of its investigation. “That’s why we’re here – to prevent the next tragedy,” she said.
“Our recommendations must be implemented, or we’ll be here again.”
Two of the four runways at the airport remained closed following the crash. Passengers have been warned to expect further disruption after Sunday’s cancellations affected the arrival of aircraft and flight crews.
The crash happened during the Labor Day holiday weekend, one of the busiest travel periods in the US.
Amazon said it was “heartbroken” by the loss of life and that it was working closely with authorities.
21 Air, the company operating the aircraft, expressed its condolences and said it was co-operating with the investigation.
