WASHINGTON (AP) _ A 1991 plane crash in Colorado that killed 25 people was the result of the same rudder problem responsible for a crash three years later outside Pittsburgh that killed 132 people, federal investigators said Tuesday.
The finding confirmed what investigators had surmised in an earlier report about the March 3, 1991, crash of United Airlines Flight 585 just outside Colorado Springs Municipal Airport.
The two crashes and a nonfatal incident in 1996, all involving Boeing 737s, led federal investigators to test the rudder of that model and determine that all three were caused when the hydraulics that operate the rudder jammed.
Boeing has since redesigned and retrofitted all the rudders on its 737s operating in the United States.
The Colorado Springs crash occurred when a Boeing 737 was attempting to land in clear conditions. The plane rolled and slammed nose-first into a field four miles short of the runway.
All 20 passengers, two crew members and three flight attendants were killed.
After a 21-month investigation, the National Transportation Safety Board could not say definitively what caused the crash but said it most likely was due to a steering malfunction or severe weather.
Although the weather was clear at the time of the crash, investigators speculated that wind coming off the surrounding mountains could have created a ``rotor'' _ a strong downward wind similar to a tornado but less severe.
In September 1994, all 132 people on board were killed when a USAir Boeing 737 bound for Pittsburgh spiraled 6,000 feet into a gully and burst into flames in Aliquippa, Pa., about 19 miles northwest of Pittsburgh.
On June 9, 1996, pilots of an Eastwind Airlines Boeing 737 had trouble landing in Richmond, Va., but managed to bring the plane in safely.
The three incidents prompted the NTSB to look at the rudder system and issue a report in 1999 citing rudder failure as the most likely cause of all three. After the report, Boeing agreed to redesign the rudder.
Those findings were incorporated into the revised report on the Colorado Springs crash. The report was approved by the board in March and released Tuesday.
The NTSB said since the loss of rudder control occurred less than 1,000 feet off the ground, the pilots could not have been expected to regain control of the aircraft.