The Gulfstream GVI (G650) jet was taking off with a simulated engine failure when it crashed April 2, 2011, in Roswell, N.M.
Performance issues that arose during two earlier test flights weren't properly evaluated, safety experts testified Wednesday at a National Transportation Safety Board hearing.
"Two prior close calls should have prompted a yellow flag but instead of slowing down to analyze what had happened, the program continued full speed ahead," NTSB Chairwoman Deborah Hersman said in her opening comments.
"This crash was as much an absence of leadership as it was of lift," she added.
Video footage of the two earlier test flights, which took place in November 2010 and March 2011, was shown during Wednesday's hearing.
Hersman noted that accident investigators have seen crashes involving airline pilots and truck drivers who pushed their limits to arrive at a final destination.
"In this investigation, we saw an aggressive flight test schedule and pressure to get the aircraft certified," she said. "Assumptions and errors were made, but they were neither reviewed nor evaluated when review data was collected."
The hearing, held in Washington, D.C., was streamed online. Testimony was
Hersman said at the close of the hearing that Gulfstream recognized that many changes needed to be made, and has begun to implement them.
The company has taken several steps to improve the plane and its testing program since the accident. Those steps include the appointment of an aviation safety official who reports directly to the firm's president and enhanced communication throughout the company, Gulfstream spokeswoman Heidi Fedak said.
The aircraft received its certification from the Federal Aviation Administration in September, and Gulfstream is preparing to deliver it to customers by the end of this year, Fedak said.
The probable cause of the crash was that the plane stalled takeoff and then it rolled, the NTSB said in a statement after Wednesday's hearing. The board found that the crash resulted from Gulfstream's inadequate investigation of such problems during the previous test flights and incorrect assumptions about takeoff speeds.
Gulfstream identified the four Savannah employees killed as test pilots Kent Crenshaw and Vivan Ragusa; and technical specialists David McCollum and Reece Ollenburg.
Hersman said "we can't change what happened" the day the jet crashed, "but we owe it to the four flight test professionals who lost their lives to make sure we learn from it."