UPDATE 12/22/10
PARKERSBURG, W.Va. (AP) -- Federal investigators say a modified oxygen system is the probable cause of a fatal airplane crash in West Virginia last year.

The National Transportation Safety Board says the pilot made improper changes to the single-engine Cirrus SR-22's system. As a result, he was deprived of oxygen and became incapacitated.

The plane crashed July 30, 2009, in a remote wooded area in Jackson County. The pilot, 61-year-old William Huff of Indiana, was killed.

Huff was returning to an airport in Indianapolis, Ind., from Nebraska when air traffic controllers lost contact after giving him clearance to descend. The plane continued flying until it ran out of fuel and crashed.

Pilot Chuck Huff was killed, but it wasn't clear if he died before the crash or as a result of it.

In a preliminary report, the NTSB says the 61-year-old Indiana man was incoherent and breathing heavily just before controllers lost contact with him near Indianapolis.

The plane had left York, Neb., and was expected to land at Eagle Creek Airpark near Indianapolis. But the plane flew on for more than 300 miles before crashing near Ravenswood, 50 miles north of Charleston.

Huff was the only person on the plane.

The NTSB said Huff was an experienced pilot who passed an air worthiness physical just days before the July 30 crash.

A final report isn't expected for several months.

It happened just after 10 p.m. in the area of Skull Run Road, which is just north of Ravenswood.

A family member tells WSAZ.com that 66-year-old Chuck Huff of Indianapolis, Indiana died in the crash. He was the only person on board.

Arlene Salac with the FAA tells WSAZ.com that the Cirrus SR-22 plane with tail number N581DS took off from Nebraska at about 6 p.m. and was headed to Eagle Creek, Indiana. Flight control lost contact with the pilot at about 8 p.m.

Salac says they believe the pilot became incapacitated during flight and the pilot overshot his approach. The FAA tracked his flight path and estimated he’d run out of fuel near Henderson, W.Va. The crash happened 12 mile NE of Henderson. ( click here to see the plane's flight path )

Two National Guard F-16 jets were sent up to track the plane after it passed the airport near Indianapolis, according to the North American Aerospace Defense Command. The fighter pilots attempted to make contact with the pilot, even shooting off flares to try to get his attention, but they say he appeared to be unconscious. The F-16s followed the plane until it went down.

Brian Rayner with the NTSB arrived at the scene Friday afternoon. He told WSAZ.com that information he's gathered indicated that the pilot was very experienced and the plane was only about a year old.

Rayner also says it was impossible to predict where the plane might have crashed. He says the aircraft had enough fuel to make it to the Atlantic Ocean, but believes something, possibly weather, caused the plane to kick out of autopilot and crash in Jackson County.

Walter Smittle, Director of Jackson County Emergency Services, says the crash happened in a wooded area near the top of a hill, and left behind a large debris field. He says the concern from the scene was a parachute device on the plane that deploys during an emergency because it uses explosives when activated. A 200 yard perimeter was immediately set up around the plane.

No homes in the area were evacuated, but Skull Run Road was shut down for a period after the accident, according to Smittle.

The plane is registered to Sequoia Airways LLC out of Avon, IN.

It happened just after 10 p.m. in the area of Skull Run Road.

911 dispatchers say crews have arrived at the scene, but no information is being released at this time.

Walter Smittle, Director of Jackson County Emergency Services, says the 911 center has received multiple reports of a plane down. He is on the way to the possible crash site.

No word yet what type of plane might have been involved.

Lt. Mike Cadle with the West Virginia National Guard say all of the planes based in W.Va. are accounted for.

WSAZ has a crew on the way to the scene. Keep clicking on WSAZ.com for more information.