Sloppy maintenance and inadequate procedures for calculating and distributing weight led to the crash of an Air Midwest plane in North Carolina that killed 21 people last year, investigators said on Thursday.

In a sharply critical report, the National Transportation Safety Board found that missteps by a contractor were made worse by Air Midwest's use of inadequate weight and balance standards, which left the Beech 1900D turboprop overweight and tail heavy.

"There were a lot of mistakes made here," said Mark Rosenker, the vice chairman of the safety board. "I'll call it sloppy."

John Goglia, a senior board member and former mechanic, said the worst maintenance-related case he had investigated was the 1996 ValuJet crash in Florida. "But this accident, with the sheer number of people who failed to do their job, set a new low," he said.

Brian Gillman, a spokesman for Air Midwest parent Mesa Air Group, said the company was reviewing the safety board's findings and would not comment further.

Doomed Flight 5481 to Greenville, South Carolina, operated for US Airways as a commuter flight by Air Midwest, climbed after takeoff from Charlotte Airport at a dangerously steep angle, rolled left and crashed next to a maintenance hanger. All 19 passengers and two crew members died.

Investigators quickly concluded that cables controlling the plane's elevator, which regulates aircraft pitch, were improperly adjusted.

Records show that mechanics for Raytheon Aerospace, a contractor for Air Midwest, had performed the work in West Virginia two days before the accident. The mechanic who adjusted the cables had not done that work previously.

Investigators said the mechanic had little guidance and steps were skipped, including one that would probably have caught the misaligned cables and prevented the crash.

Investigators also found the work was not adequately supervised. They raised questions about record keeping, Air Midwest maintenance training and oversight, and the clarity of instructions in the aircraft's maintenance manual, which was written by manufacturer Raytheon Aircraft, a unit of Raytheon Co.

Raytheon Aerospace, which changed its name last year to Vertex Aerospace, is not related to Raytheon Co. It no longer does work for Air Midwest.

Compounding the mechanical problem, investigators said, were inadequate standards at Air Midwest for assessing the weight and balance of passengers and luggage. This led to "substantially inaccurate" calculations.

The Beech 1900 had flown several times after the maintenance but not with the type of load it was carrying on its final flight. The plane was 600 pounds (272 kg) overweight and tail heavy. But investigators said the plane, with a fully functioning elevator, should have been able to fly.

(Reuters)