The plane in which two young Waipahu men were lost July 27 had been flying through clear night skies when it encountered severe weather off north Moloka'i and crashed, according to a National Transportation Safety Board preliminary report.

The report did not conclude that weather caused the crash. A final report that includes a probable cause for a crash normally is published months or even years after the event.

A witness on north Moloka'i described the plane's lights descending out of the clouds, going fast.

"The witness noted that the airplane lights were wobbling one over the other and the engine was revving loudly," said the report, which was based on the work of NTSB investigator Nicole Charnon. It was not clear whether the wobbling lights might have indicated the aircraft was in a spin.

The report on the loss of the plane indicated the descent ended in a crash into the ocean about a mile off Moloka'i's northern cliffs. While no wreckage and no survivors have been found, the evidence seems conclusive that the plane crashed, the report indicates.

"The airplane sank and is presumed destroyed. ... The certified flight instructor and the pilot receiving instruction are presumed to have been fatally injured," said the report, prepared by Charnon.

Flight instructor Joshua Tabisola, 25, and student pilot Jacob Jacob, 23, both of Waipahu, had checked out the Cessna 177B from Anderson Aviation at Honolulu Airport. They took off a few minutes before 8 p.m., headed for Maui's Hana Airport.

Both were certified pilots with instrument ratings. Tabisola was assisting Jacob in obtaining his commercial flying license.

They flew from O'ahu to Moloka'i, and the flight appeared uneventful as they passed Moloka'i's western end offshore at an elevation of 5,000 feet, and then passed offshore from Kalaupapa in the middle of the north side of the island.

Five miles east of Kalaupapa, radar and witness reports indicated there were clouds and rain. The plane began a series of maneuvers, turning south toward the cliffs, then south-southwest, then south again. Its elevation was now 5,100 feet and the plane was flying at roughly 100 mph over the water.

Suddenly, individual radar sweeps by the Navy's Fleet Area Control and Surveillance Facility showed something seriously wrong. One sweep showed the Cessna had dropped to 3,700 feet above sea level and its speed across the surface had dropped to 57 mph. The next sweep showed it had dropped to 1,400 feet and was going just 35 miles an hour. A final sweep showed it at 200 feet above the surface. The aircraft did not reappear on radar.

The NTSB report said rain was visible on Navy radar over Moloka'i, and that a witness report to the Coast Guard said the rain and clouds moved through the area quickly, leaving weather clear again not long afterward.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.