The decision was revealed Monday in a quarterly filing by corporate parent Alaska Air Group Inc. with the Securities and Exchange Commission.
An aide to assistant U.S. attorney Matt Jacobs confirmed the decision to The Seattle Times but would not elaborate. Company officials would not comment Monday to the Times or The Seattle Post-Intelligencer.
The filing stated that the U.S. attorney's office last month concluded that "the evidence does not warrant the filing of criminal charges and it has closed its investigation."
The Alaska Airlines MD-83 crashed in the Pacific Ocean off Port Hueneme, Calif., on Jan. 31, 2000, on a flight from Puerto Vallarta, Mexico, to San Francisco and Seattle.
Over 20 minutes, the plane went into two steep dives, flew upside down and plunged into the Pacific Ocean off Port Hueneme, California, northwest of Los Angeles.
The National Transportation Safety Board in December blamed shoddy maintenance for the failure of the plane's jackscrew, a tail component that helps move the jet's stabilizer and sets the angle of flight.
"There was no effective lubrication on the (parts)," the NTSB found. "The excessive and accelerated wear of the (parts) was the result of insufficient lubrication, which was directly causal to the Alaska Airlines flight 261 accident."
All but one of the 88 wrongful death lawsuits filed by crash victims have been settled. Alaska Air conceded legal liability for the crash and Boeing Co., which merged with the plane's manufacturer McDonnell Douglas in 1997, agreed not to contest liability.
The remaining lawsuit, in which only the amount of damages remains at issue, is pending in U.S. District Court in Los Angeles.
Alaska Airlines admitted liability under an international treaty covering the flight and agreed to pay whatever compensatory damages a jury awards.
Boeing, which previously said Alaska failed to maintain the plane properly, decided not to contest liability any longer because it wanted to bring about an "expeditious resolution," company spokeswoman Liz Verdier said.
In May, Judge Charles R. Breyer, who is overseeing the litigation, ruled out punitive damages against Boeing. Alaska Airlines is immune from punitive damages under an international treaty.
The airline may later seek compensation from Boeing. Alaska Airlines previously blamed Boeing-approved grease and flaws in the design and maintenance plan for the ill-fated MD-83, a theory rejected in December by the NTSB.
The federal probe that has now closed was reopened after the NTSB's final report on the crash.
The U.S. Attorney probe began in 1998 after complaints about maintenance at Alaska Airlines' Oakland facility. It was later expanded to include the crash of Flight 261.
Eventually, the initial charges were settled as a civil matter, and the part of the probe dealing with the Flight 261 crash was suspended. The U.S. Attorney, however, said it might be reopened, and it was reopened after the NTSB report.
The NTSB found that the airline's decision to lengthen the period between lubrications of the parts in question — and the Federal Aviation Administration's approval of that move — "increased the likelihood that a missed or inadequate lubrication would result in excessive wear … and, therefore, was a direct cause of the excessive wear and contributed to the Alaska Airlines flight 261 accident."