PITTSFIELD – Alton E. “Chuck” Cianchette was navigating by vision, not his plane’s navigational instruments, when he crashed in bad weather last January, according to a report by the National Transportation Safety Board.

Investigators also found no evidence that the former state senator filed a flight plan or sought a weather briefing before his plane crashed in Kentucky.

Cianchette, who was 69 and an experienced pilot, apparently was flying his 1948 single-engine Cessna under visual rules before his plane struck a snow-covered hill Jan. 18, the report released Wednesday said.

He was headed to a home in St. Petersburg, Fla., to join his wife, Helen. He died from of injuries he suffered in the crash.

A toxicology report conducted by the Federal Aviation Administration also showed medication called chloroquine present in Cianchette’s blood and liver. The drug is used to treat and prevent malaria. Health officials advise users to use caution when operating machinery while on the medication.

Witnesses said they saw the plane flying low, at altitudes of between 600 and 800 feet, as it passed in and out of snow showers in mountainous terrain, the safety board report says.

On a clear day, an airplane like Cianchette’s 1948 Cessna would be expected to sustain altitudes at around 1,500 feet. In clouds, the aircraft’s instrument panel would be used for navigation.

“[Witnesses] heard an airplane make two passes overhead; an engine revved to full power, then silence,” according to the NTSB report.

Cianchette apparently was trying to stay under the clouds to maintain visual contact with the ground when he ran into weather that called for the pilot to use flight instruments to guide the plane.

The report also said airplane fuel was detected at the crash site, indicating that the plane did not get lost in the clouds and run out of fuel before the crash.

The plane’s alternator, retained for further examination, was found to be in operating order when the crash occurred. According to an FAA inspector, there was no record of a weather briefing on Cianchette’s plane, nor was there a flight plan.

Cianchette, who helped turn Cianbro Corp. from a family business into one of New England’s largest general contractors, had four decades of flight experience.