The faulty data allegedly caused one helicopter to crash in 2008, killing nine people, The (Portland) Oregonian reported Monday.
Steven Metheny, 42, the former vice president of West Coast operations for Carson Helicopters, and Levi Phillips, 45, his former maintenance director, are accused by a federal jury in Medford of falsifying the weight and takeoff power of helicopters purchased from the company as part of a $20 million "call-when-needed" contract.
The information was included in charts used by flight crews to calculate the total weight of firefighters and their gear the helicopters could carry.
One of the Carson helicopters crashed in 2008, killing seven firefighters and two people and injuring four other people.
National Transportation Safety Board investigators said the Sikorsky S-61N helicopter weighed more than 1,600 pounds in excess of what the pilot thought.
Witnesses said the craft rose no more than 40 or 50 feet before clipping the tops of trees and crashing.
The incident is considered one of the nation's worst firefighting air crashes.