A Newport Beach man agreed to plead guilty to piloting an Alaska Airlines plane while he was under the influence of alcohol, the U.S. attorney’s office said Tuesday.

David Hans Arntson, 62, acknowledged as part of the plea agreement filed in federal court that he was an alcoholic for a “substantial” portion of his career as an airline pilot.

In exchange for pleading guilty to a felony count of operating a carrier while under the influence, several other charges against Arntson are being dropped, prosecutors said.

Prosecutors and Arntson’s attorney agreed that he should be sentenced to a year and a day in federal prison, followed by three years of supervised release. Arntson was facing up to 15 years in federal prison.

U.S. District Judge Cormac Carney will decide Arntson’s sentence at a future hearing. A date has not been set.

According to court documents, Arntson piloted two Alaska Airlines flights on June 20, 2014. The first was at 6:21 a.m. from San Diego to Portland, Ore. After a brief layover, he piloted a flight from Portland to Orange County.

After he landed at John Wayne Airport, Arntson was selected for random drug and alcohol testing by Alaska Airlines.

Breath tests conducted 15 minutes apart in an airport restroom indicated that Arntson had blood-alcohol concentrations of 0.134% and 0.142%, according to court records.

“Those percentages were well above the federal limit of 0.04% for pilots,” the plea agreement states.

Arntson told investigators that he didn’t understand the test results since he hadn’t consumed alcohol that day. Arntson said he ordered a beer with dinner the night before the flight from San Diego but took only a few sips.

Arntson, who had worked for Alaska Airlines since 1982, was removed from “safety-sensitive duties” the day of the tests, according to the airline. He later retired because of medical issues.

“Thankfully, Mr. Arntson was never involved in an accident, but his conduct could have resulted in tragic consequences,” U.S. Attorney Nicola Hanna said in a statement. “Very few people will ever hold the lives of so many people in their hands at one time.”

hannah.fry@latimes.com

Twitter: @HannahFryTCN