HONOLULU (AP) — A witness saw a medical transport plane that disappeared on a flight between Maui and the Big Island go into a spiraling descent and hit the ocean, according to a preliminary report released Thursday by the National Transportation Safety Board.

The plane's wreckage sank in the Maui Channel with an estimated depth of 6,000 feet (1,830 meters), the report said.

The three people on board — an airline transport pilot, a flight paramedic and a flight nurse — are all presumed dead, the report said.

Last month, the Hawaii Life Flight emergency fixed wing plane went off radar while en route to pick up a patient, a statement from Global Medical Response said. The patient was not on board.

The flight departed Maui's Kahului airport at 8:53 p.m. on Dec. 15 and was headed to Waimea on the Big Island to pick up a patient to be taken to Honolulu.

According to the report, the pilot was in contact with the Honolulu Air Route Traffic Control Center and was following instructions. The plane's final radio transmission was believed to be the pilot saying, “Hang on,” the report said.

A witness flying a small plane from Hilo to Honolulu saw the aircraft as it “entered a spiraling right descending turn, which steepened as the descent increased,” the report said. “The witness said that he watched the airplane continue to descend until it impacted the surface of the water.”

The witness then lost sight of the airplane's lights.

The report includes factual information but not a probable cause. That is typically included in a final report, which could take a year or two to complete.

The Coast Guard searched with boats, a helicopter and a cargo plane. Portions of airplane wreckage were found floating near the medical flight's last known location, the report said.

The search was suspended on Dec. 19 without locating the plane or its occupants.

Global Medical Response had temporarily paused Hawaii Life Flight transports, prompting Gov. Josh Green to issue, and later extend, an emergency proclamation allowing the state to supplement Hawaii’s medical flight capacity in the interim.

The proclamation allows the Hawaii National Guard to fly Blackhawk helicopters to transport patients. It also allows AirMed International, a sister company of Hawaii Life Flight, to bring a plane and crew members to Hawaii from the U.S. mainland.

The emergency relief period for the proclamation was scheduled to continue through Friday.

Many hospitals on Hawaii’s more rural islands are small and offer limited medical services compared to Honolulu’s larger hospitals. Patients with more serious, urgent conditions often need to be transported to Oahu for care.

Hawaii Life Flight identified the pilot of the medical transport plane as Brian Treptow, The Maui News reported. The flight nurse was identified as Courtney Parry and the flight paramedic as Gabriel Camacho.

“We truly feel the love and support from not only our family and friends but from the community at large,” Camacho’s mother said in a statement. “Gabriel loved what he did, and he was well aware of the risks."

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