The Federal Aviation Administration and the National Transportation Safety Board are investigating Saturday's accident at Modesto Airport in which the same plane made three emergency landings in three hours.
A passenger was seriously injured when she jumped out of the moving plane, and the pilot suffered from smoke inhalation.
Ian Gregor of the FAA indicated that officials were surprised that pilot Wil-liam Supan, 52, of Pleasanton would try to take off a third time after having been forced to land twice because of smoke in the cockpit.
"We're going to have a long talk with Mr. Supan," Gregor said.
Wayne Pollack of the NTSB said it would be about 30 days before a final report on the cause of the accident is finished. Pollack said the physical examination of the plane was almost complete and there had been one interview with Supan. He said Supan had 10 days to submit a written report. There will be more interviews with firefighters at the scene, Pollack added.
Efforts to reach Supan on Tuesday were unsuccessful.
An FAA official not connected to the investigation said all parts used in an airplane must be traceable to a certified airplane parts manufacturer. He said even if two parts look identical, it is unlikely they will perform the same unless they fit airplane or military specifications.
After he was forced to land the first time, Supan told Sky Trek workers he had to replace an exhaust hose clamp and that he was going to Wal-Mart to get it.
When the plane filled with smoke again, he reportedly said the exhaust hose had been cut. He replaced the hose and tried to take off again.
When an FAA technician examined the wreck, the exhaust hose and clamp were still on the engine, but it appeared the exhaust hose was cut in two.
Gregor questioned the wisdom of flying without having a certified mechanic check the plane.
Licensed pilots are allowed to work on their planes for only the most minor preventive maintenance. Gregor said a pilot would be allowed to do very basic, simple things, "like what drivers can do for their car, like check the oil."
A check of the FAA database showed Supan was a pilot and not a rated mechanic.
Jinhua Lin, the woman who jumped from the plane, remained in acute care Tuesday. She suffered a broken leg and abrasions. There were no updates available on her condition.
Bee staff writer Roger W. Hoskins can be reached at firstname.lastname@example.org or 578-2311.