"In my 40 years as a firefighter here in Hawaii, this is the most tragic aircraft incident that we've had," Neves said.
The plane was engulfed in flames when firefighters made it to the crash site about an hour drive from Honolulu, Neves said. The victims were not identified.
Two Federal Aviation Administration inspectors went to the crash site Friday and investigators with the National Transportation Safety Board that will investigate the crash were expected to arrive Saturday evening, said safety board spokesman Eric Weiss.
The plane with two turboprop engines was manufactured in 1967, FAA records said.
The phone for Oahu Parachute Center went unanswered Saturday.
On its web site, the company says the jumps that it offers on Hawaii are "a magical experience. There really is no better place in the world to skydive." Its tandem jumps are listed for prices ranging from $170 to $250.
Videos from the company's Facebook page show jumps from the same Beechcraft King Air that crashed, with customers strapped to employees and dropping from a side door of the aircraft from 10,000 feet (3,000 meters) or higher, with the Pacific Ocean and the Oahu's green mountains far below.
Dillingham Airfield is used mostly for skydiving and glider flights. Hawaii shares the airfield with the Army, which uses it for helicopter night-vision training.
- AP