David Alan Anderson, who allegedly carried a knife onto an airplane and threatened a passenger and police in Salt Lake City, Utah, Sept. 18, 2011.

SALT LAKE CITY — A Utah man accused of smuggling a knife onto an airplane and threatening to kill police pleaded guilty to a reduced charge in federal court Thursday.

David Alan Anderson entered a guilty plea to a single count of possessing a dangerous weapon in Salt Lake City's U.S. District Court.

Prosecutors dropped two other felony charges in exchange for the plea.

The 60-year-old faces a maximum prison term of 10 years at sentencing April 9.

Anderson was arrested Sept. 18 after being removed from a Las Vegas-bound Delta Airlines flight in Salt Lake City. Authorities said he threatened to kill his seatmate in a dispute over a shared armrest.

Police later found Anderson had a knife in a carry-on bag and was arrested.

"I'm going to kill you in front of your children," Anderson told a police officer during an interrogation, authorities said in court papers.

Defense attorney Steven Killpack later told a judge that Anderson was a distinguished retired Salt Lake City attorney who was not taking his medications for anxiety and a biploar disorder.

A judge initially held Anderson in jail, but released him late October on the condition that Anderson undergoes mental health treatment prior to a federal trial.

On Thursday, Killpack said the plea agreement is an excellent resolution to Anderson's case.

Anderson mistakenly left a folding knife inside a briefcase and never intended to take it onto the plane, Killpack said.

A security officer monitoring an X-ray machine when Anderson came through with the knife did not see the weapon. That person was sent for further training, Transportation Security Administration spokeswoman Lorie Dankers has said.