NEW YORK — Federal officials on Wednesday released images of a doomed New York City sightseeing helicopter as it broke apart in midair last month, killing six people.

The series of still photographs taken from surveillance camera video shows the fuselage, containing the engine and rotors, separating from the helicopter’s tail. The rotor blades and the transmission then detach from the cabin that’s carrying the passengers and the pilot.

The images were included in the preliminary report about the flight released by the National Transportation Safety Board.

“Several witnesses described hearing several loud ‘bangs’ emanating from the helicopter before it broke up and descended into the river,” the report says.

Justin Green, an aviation lawyer and former Marine helicopter pilot, said the sequence of images shows the helicopter yawing severely and the tail boom failing, suggesting it was most likely struck by the aircraft’s main rotor blades while in flight.

“It’s clear that some mechanical issue precipitated the breakup,” he said. “We still do not know the exact issues, only potential causes.”

The initial NTSB report, which runs about six pages, does not address the initial cause of “the in-flight breakup of the aircraft,” he said. That will likely be determined by a forensic examination of the wreckage itself, including the rotor blades, the engine and transmission.

Federal Aviation ministration records show the aircraft, a Bell 206L-4, was built in 2004 and had a maintenance issue last September involving its transmission assembly.

The NTSB said previously that the aircraft, which was operated by tour company New York Helicopter, was not equipped with any video or data recording devices.

But on Wednesday, it said photos taken beforehand show that the pilot, Seankese Johnson, was wearing computer-augmented sunglasses, which would have had video and audio recording capability. The glasses have not been recovered, however.

Johnson, a 36-year-old former Navy SEAL, received his commercial pilot’s license in 2023 and had logged 790 hours of flight time, according to the NTSB report.

But he didn’t appear to be particularly experienced flying a Bell 206L-4, according to Al Yurman, a retired NTSB investigator, who noted the report found he had fewer than 50 hours of flight in that type of aircraft.

“It’s quite sophisticated for that type of work,” Yurman said. “I would prefer to have someone more experienced but we’ll know more when the full report comes out.”

The report said Johnson worked a “10 days on/10 days off schedule” and the April 10 flight was his first day back after 10 days off. The flight was also the eighth of the day for the pilot and the helicopter.

The aircraft was on a typical tour, departing from the downtown heliport by Wall Street around 3 p.m. and flying north along the Manhattan skyline before heading south toward the Statue of Liberty.

Less than 18 minutes into the flight, witnesses saw the tail and main rotor break away and smoke pouring from the spinning helicopter.

In recent years, New York Helicopter, the tour company, went through bankruptcy and faced ongoing lawsuits over alleged debts.

The company has said it is cooperating with authorities in the investigation. No one answered the phone at its office or responded to an email seeking comment on Wednesday.

The crash was among a recent string of aircraft disasters and close calls that left some people worried about the safety of flying in the U.S. It also revived concerns about the popular and costly aerial tours over New York City.

Five commercial sightseeing helicopters have gone down in the rivers around Manhattan since 2005 as a result of mechanical failure, pilot error or collision, killing 20 people.

The April 10 crash killed a prominent family from Barcelona, Spain: Agustín Escobar, 49; Mercè Camprubí Montal, 39; and their children Victor, 4, Mercedes, 8, and Agustin, 10.

Officials have said Escobar, global CEO of rail infrastructure at Siemens Mobility, was in the New York area on business.

Montal, who worked for Siemens Energy and was the granddaughter of a former president of the famous Barcelona FC soccer club, flew in with their children to meet him.

Mercedes would have turned 9 the day after the crash.