Steven Slater, 38, avoided jail under a plea bargain that requires him to undergo counseling and substance-abuse treatment for at least a year. He must also pay $10,000 in restitution to JetBlue.

Queens District Attorney Richard A. Brown said Slater wasn’t just fed up with his job or angry at a passenger when he stormed off the plane. He said investigators believe Slater was drunk and suffering mental problems, though the prosecutor wouldn’t give specifics.

Slater spoke calmly as he pleaded guilty to criminal mischief and attempted criminal mischief. Afterward, a smiling, upbeat Slater said: “At the end of the day, I’m a grown-up and I must take responsibility for my actions.”

Slater admitted he pulled the emergency chute Aug. 9 on a flight from Pittsburgh after it landed at Kennedy Airport. He went on the public-address system, swore at a passenger who he claimed treated him rudely, grabbed a beer and slid down onto the tarmac. He had a bandage on his forehead, apparently after he got hit with a piece of luggage before takeoff.

Slater’s departure made him a folk hero to put-upon workers everywhere who have fantasized about quitting in a blaze of glory. He was a topic on TV shows, on the Internet and on the front pages of newspapers, with many cheering him for standing up to the often-inhospitable world of airline travel, and others accusing him of childish and dangerously reckless behavior.

Slater was initially charged with criminal mischief, reckless endangerment and trespassing and faced up to seven years in jail. Under the plea bargain, if he fails to complete the counseling and treatment to a judge’s satisfaction, he will get one to three years behind bars.

“Mr. Slater felt somewhat humiliated after what he perceived as degrading working conditions, and he had a level of rage at the time that was perhaps exacerbated by alcohol intoxication and maybe some other contributing stress factors,” the district attorney said. “As a result, I think he overreacted when he was confronted by what he perceived as a rude passenger.”

Brown said activating the escape chute “was no laughing matter,” and he scolded Slater — and the public — for not taking his actions more seriously. The district attorney noted that it cost $25,000 to fix the slide and that the plane had to be taken out of service, causing flight delays.

The airline has also pointed out that someone on the ground could have gotten hurt. Emergency slides deploy with potentially deadly force.

JetBlue had no comment on the plea.

Slater, who has no criminal history, has said he cracked under pressure because of his terminally ill mother, recently deceased father and health problems of his own, including HIV.

A mental-health evaluation determined that Slater has a clinical disorder and alcohol-abuse problems. The district attorney did not specify what his disorder was.

JetBlue suspended Slater after the incident, and he resigned in September, leaving him unemployed. He had worked at JetBlue for about three years, though he spent nearly two decades in the airline industry.

Slater said weeks ago that he wanted to continue working in the airline industry, but Howard Bragman, his publicist, would not comment on his future.

His 15 minutes of fame are not quite over: In a homage to Slater, several businesses are selling a new costume for Halloween: the disgruntled flight attendant.

“It’s a blue steward shirt with a light blue tie and it comes with a Band-Aid for your forehead,” said Todd Kenig, chairman of Ricky’s NYC.