At the time of the crash, the company had only a few blue harnesses in use.

Cutting the Harness

Likewise, the company’s pilots raised concerns about the tethers used to secure the passengers, via their harnesses, to the interior of the helicopters. It was difficult for passengers to reach the point at which the tethers fastened to their yellow harnesses, and, even if they could reach the connection, it would be difficult for them to disconnect the carabineers that connected the tethers to the harnesses on their own, according to the pilots who worked with FlyNYON. So each passenger was provided a hook-shaped blade, marketed as a seatbelt cutter, that they were instructed to use to sever the tether in case of an emergency that required them to extricate themselves.

A safety video played for passengers before they went on trips showed people using the cutters to easily slice through the tethers, according to people who viewed it. But the tethers in the video were not the same ones being used by FlyNYON. And when employees tested the equipment that was in use in November, they found it extremely difficult to sever the tether using the cutter, according to the former FlyNYON official.

Managers from FlyNYON were present for the test, the former official said. But it was not until February that the company began formally considering a plan to order new tethers and cutters that would allow for easier slicing, according to the emails. The minutes of a late February meeting highlight a discussion about “researching and procuring a new cutter for the tethers which we will be testing shortly. There is also a new style of tether we are looking into as well. This will need to be included in the safety video.”

On March 7 — just four days before the crash — the company planned to discuss a “final decision” on the new tethers and cutters, according to the emails.

It is unclear if FlyNYON purchased the new equipment, but, even if it did, the new tethers and cutters were not deployed on the fatal March 11 flight. Instagram videos posted by the passengers before liftoff show them wearing the yellow harnesses.

A preliminary report by the N.T.S.B. indicated that the pilot, Mr. Vance, told investigators that he had “pointed out where the cutting tool was located on their harness and explained how to use it” before taking off.

While hovering over Central Park, he told them, the single-engine helicopter, an AS350 B2 model made by Airbus, suddenly lost power. When he reached down to cut the flow of fuel as he prepared to put the aircraft down in the river, he saw that the fuel cutoff lever had been tripped and the tether of his front-seat passenger was under it. That observation suggested that the passenger’s movement may have caused the crash, though federal investigators have not reached a conclusion about the cause.

After the crash, Dave Matula, a pilot who used to fly for FlyNYON who stopped last year, wrote on Facebook that the fatalities were a “horrible but 100 percent preventable event.”