Federal agents began combing the wreckage Saturday of a twin-engine, turboprop airplane that plunged 28,000 feet into a remote wildlife reserve southwest of Bunnell, killing two people from the Midwest.

A National Transportation Safety Board agent investigating the site said thunderstorms may have played a part in the crash, though no official conclusion will be made for six to 12 months.

Ward Walter, 66, the pilot and founder of a medical disposal company, was flying with his wife, Barbara, 64, when the Mitsubishi MU-2 plane went down Friday. They were traveling from Plainwell, Mich., to a home they owned in the Bahamas.

"What we're looking at really is the man, the machine, the environment," said Robert Gretz, an investigator from the agency's New Jersey office.

Agents will study the piloting experience and record of Walter, Gretz said. They will inspect the wreckage for any hints of mechanical failure, and will peruse radar and weather data to see how the elements might have influenced the crash.

Preliminary findings will be available in five days, Gretz said.

Early data from control towers indicates the Walters encountered adverse weather and veered off course, Gretz said. The pilot struggled to keep the aircraft from losing altitude, and the plane disappeared from the radar about 1:40 p.m. Friday.

The first task, Gretz said, will be dismantling and removing the wreckage, which will take about two weeks.

The bodies of the crash victims were transported from the site Saturday, Flagler County officials said.

Air traffic officials have reported that the plane plummeted from 28,000 feet to 8,000 feet in one minute. The aircraft slammed into the ground so hard, it burrowed several feet into muck.

An aviation expert said the rapid nosedive combined with debris found a mile from the wreckage are strong evidence the plane broke apart in the air.

"Sounds like an in-flight breakup," said Bob Breiling, who founded a Boca Raton company that tracks jet and turboprop accidents. Breiling has flown jets for the U.S. Navy, a commercial airline and corporate clients.

Two things can cause a plane to bust apart in the air: heavy turbulence and the pilot pushing the aircraft beyond a safe speed, he said. It appears that Walter received guidance from air traffic controllers about steering around the storms, Breiling said. The big question is whether the instructions were flawed, or whether Walter failed to follow them precisely.

Breiling, who works with Mitsubishi, said a company official told him Walter had owned the MU-2 a long time and had logged about 3,000 hours as a pilot, giving him considerable experience.

The MU-2 has about twice the accident rate of the average turboprop, Breiling said, and not because the plane is mechanically flawed.

Because it's an older model, it can be bought at a bargain price, even though the wing design makes it faster and more challenging to handle than most turboprops, Breiling said. Pilots aren't required to take simulator training for turboprops, so they can wind up flying MU-2s unprepared for its nuances, he said.

Businesses often buy the planes to haul cargo, he said, and they'll typically hire one pilot instead of two. Without a backup, a pilot can become overwhelmed in a crisis, Breiling said

Scott Sobel, a Mitsubishi spokesman who visited the crash site Saturday, said the MU-2s are sturdy, reliable planes.

When the planes are maintained properly and the pilots have adequate training, the MU-2's accident rate is in line with other turboprops in its class, Sobel said.

scott.wyland@news-jrnl.com