WASHINGTON (AP) _ The National Transportation Safety Board says cocaine use by the pilot of a Colorado commuter flight contributed to a crash that killed nine people.

The five-member board reached the conclusion after a year's investigation into the Jan. 19, 1988, crash of a Trans-Colorado flight into Durango, Colo., in which the pilot, co-pilot and seven passengers died. Eight passengers survived.

The decision came even though investigators said the cocaine found in pilot Stephen Silver's blood and urine was insufficient to make him ''high'' during the flight and co-pilot Ralph D. Hardy was controlling the Fairchild Metro 3 aircraft before it crashed into a hill five miles short of the Durango runway.

''Contributing to the accident was the degradation of the captain's performance resulting from his use of cocaine before the accident,'' the board said. It blamed both ''the first officer's flying and the captain's ineffective monitoring of an unstabilized approach which resulted in a descent below the published descent profile.''

The board said the plane began its descent at too high an altitude and speed to land safely.

Investigators found no problem with the aircraft or air traffic control instructions that might have contributed to the crash but raised some questions about the landing approach path the pilot chose to use.

The board asked the FAA to examine procedures that approved the steep ''slam-dunk'' approach used by the now-defunct airline, called for more FAA assistance in screening of pilots and urged greater dissemination of information about detecting drug use among airline personnel.

The board opposes random drug testing of all airplane crew members as called for in a program set up by the Federal Aviation Administration, saying it prefers testing before employment, after accidents and when warranted by a ''wide range of safety related errors.''

Investigators said Silver, 36, lied about previous drunken driving convictions to obtain a medical certification to fly and noted that co-pilot Hardy's record of training with Trans-Colorado and previous employment indicated ''deficiences in performing instrument procedures.''

The plane leased by Continental Express, a subsidiary of Continental Airlines, crashed at night in light snow.

The board staff also noted that Hardy, 42, had a history of alcoholism although no evidence of alcohol was found in either crew member's body. Family members and friends said earlier that Hardy had overcome his alcoholism.

The board, in its conclusions and recommendations, did not address drug testing, but member Jim Burnett noted board disagreement with the FAA program.

The program requires drug testing of all airplane crew members during first medical evaluations and random testing thereafter.

Medical analysis after the Colorado crash found traces of cocaine in the pilot's blood and urine, investigators said. They also said a girlfriend of the pilot reportedly claimed he had taken cocaine the night before the crash, although she refused to talk to investigators.

Board investigator Barry Strauch said evidence showed that Silver had used cocaine between 10 and 18 hours before the flight. He said there was not enough evidence to determine whether Silver was a heavy user of the drug.

Board staff member Merritt Birky, a chemical expert, said that regular use of cocaine could cause fatigue and a preoccupation with cocaine, affecting performance of a pilot long after any ''high.''

Two negligence lawsuits have been filed against Continental Airlines as a result of the crash. Both cites Silver's cocaine use. One also alleges that the airline failed to check records of both Silver and Harvey.