United Airlines is in the spotlight again, just months after CEO Oscar Munoz promised "a culture shift toward becoming a better, more customer-focused airline."

"Does United have the right people working in its front-line jobs?" asked Henry Harteveldt, founder of San Francisco-based Atmosphere Research Group, a travel industry research company. "Are they good enough in terms of evaluating the performance of these front-line employees?"

The question arises after a June 29 incident.

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Shirley Yamauchi and her 2-year-old son were traveling from Hawaii to Boston with a layover at Bush Intercontinental Airport.

On her flight from Houston to Boston, Yamauchi said United employees gave her 2-year-old's seat to another traveler. Yamauchi, who had paid for her son's seat, was forced to hold him for the roughly three-hour flight.

United Airlines has been in the hot seat since its April 9 incident in which Dr. David Dao was forcibly removed in Chicago from a United Express flight to make way for crew members traveling to Louisville, Ky.

The airline announced sweeping policy changes after that incident, including additional annual training for agents that's set to begin in August.

That training, and more, could be needed to prevent future incidents.

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Harteveldt said the incident with Yamauchi and her son could have been prevented if the gate agent, prior to boarding, asked Yamauchi if she planned on holding her son or if she had purchased a seat.

In a statement, United said it "inaccurately scanned the boarding pass of Ms. Yamauchi's son."

"As a result, her son's seat appeared to not be checked in, and staff released his seat to another customer and Ms. Yamauchi held her son for the flight. We deeply apologize to Ms. Yamauchi and her son for this experience," the statement read. "We are providing compensation as a goodwill gesture. We are also working with our employees to prevent this from ever happening again."

Harteveldt said it takes time to develop and implement training. And with industry consolidation resulting in four airlines controlling the majority of U.S. capacity, it's likely that those airlines will get more of the negative publicity.

"No airline is infallible," he said. "The challenge, though, is for these incidents to be few and far between so the airline's PR department doesn't have to keep an apology press release template on their desktop ready to issue at any given moment."

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Houston-based airline consultant Pete Garcia added that these incidents aren't only occurring at United.

"I don't think it's isolated to United," he said. "I think United is paying the price for the most visible incident of any airline in recent history."

He said employees in today's flying environment -- where long security lines, additional fees and crowded airports have created an annoying travel experience -- need training on how to defuse arguments and avoid confrontation.