After at least three tries on Monday, 62-year-old Marilyn Hartman finally mastered her technique, allegedly slipping past a document checker who was busy screening a family at Mineta San Jose International Airport in California. She then sauntered onto Southwest Airlines Flight 3785 and, an hour later, landed at Los Angeles International Airport. That’s where she got caught — by a crew member who was checking tickets.

Hartman was arrested and charged with unlawfully entering Los Angeles as a stowaway, a misdemeanor. On Wednesday, she pleaded no contest. She was sentenced to two-years’ probation and ordered to stay away from LAX unless she has a proper ticket. According to news accounts, she smiled as she left the courtroom and, when asked how she did it, refused to tell.

“I don’t think it’s wise to say why I got through,” she told reporters. “I don’t want to help the enemy. I’m first and foremost an American.”

This wasn’t her first stowaway attempt — just her first success.

Hartman had tried similar feats at least a half-dozen times this year. On three occasions she was arrested for allegedly attempting to board flights from San Francisco International Airport to Hawaii. Three other times she was arrested for loitering there, the San Francisco Chronicle reported.

The first time she managed to get through San Francisco security and onto the plane — where she was busted by a fellow traveler who had an actual ticket. Attempts No. 2 and 3 weren’t so successful — both times she was stopped by security, the Associated Press reported. She became such a regular that she was eventually hit with a restraining order. And in May, she pleaded no contest to trespassing and violating that ban after cops found her chilling at baggage claim, the Chronicle said.

So Monday, Hartman tried San Jose International. One could assume she was wearing blue — either a collared shirt or a windbreaker. She has alternated between these two uniforms in four mug shots since February. Media have called her a homeless loner bouncing between women’s shelters and motel rooms up and down the West Coast the past decade. In April, a district attorney speculated maybe she just likes being around people. She was recently referred to a treatment facility for depression.

In one instance, the same district attorney said he tried to keep one of her arrests under wraps to see whether she was motivated by media attention.

“We were trying to figure out if she enjoyed the publicity,” District Attorney Steve Wagstaffe told the San Jose Mercury News. “But now we see that had nothing to do with it — she’s persistent, if not relentless.”

Maybe so, but Hartman did tell reporters this week she’s ready to retire.

“It was stupid, and it is something that I don’t want to repeat,” she said.

Southwest Airlines told the Los Angeles Times in a statement that it was “actively investigating” Monday’s incident but declined to specify. The Transportation Security Administration (TSA) said Hartman was properly screened “to ensure that she was not a security threat to the aircraft.” Then after an initial interview, the agency told the newspaper it has made “minor modifications to the layout of the document checking area.” And San Jose airport officials maintained that public safety was “never compromised.”

After each arrest, Hartman told police she was trying to get to Hawaii, according to reports. Records obtained by the Chronicle show she was arrested in November 2010 at the Lihue Airport in Kauai in the baggage claim area. She was charged with trespassing. She never showed up for her court hearings and has since been dodging a bench warrant.