When one fiasco settles down, another begins for United Airlines — or so it seems.

On Sunday evening, a video surfaced on social media showing a man being dragged from a United plane because his trip was overbooked. This comes just weeks after United stopped two female teenagers from boarding its plane because they were wearing "form-fitting" leggings. However, they were traveling as "representatives" of the company, a United spokesperson later argued.

"Denied boarding is usually handled with a whole lot more maturity," former United Airlines parent United Continental Holdings' (UAL) Chief Executive Gordon Bethune told CNBC in an interview Monday, referring to the forced removal of the male passenger.

"[United] tries to do a professional job, but not everybody on the plane is professional," thereby creating a "scene" on Sunday evening that carried over onto social media, Bethune added. "This immature reaction disturbs us all."

The former Continental CEO, who serves on the boards of Honeywell, Sprint and formerly on Prudential Financial, said he thinks United's current chief executive, Oscar Munoz, should issue an apology for Sunday's incident and for the passengers who had to endure it. "I'm sure there will be reconciliation ... some effort to show they care about passengers," Bethune said.

"I'm sure there will be a lot of discussion [at United] about how to handle this in the future."

Shortly after Bethune's interview on CNBC, United CEO Munoz issued a statement, saying: "This is an upsetting event to all of us here at United. I apologize for having to re-accommodate these customers. Our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened."

But for many airlines, incidents like Sunday's come as no surprise, one social media and brand expert said.

"The thing about airlines is they have a low happiness level to begin with," Andy Swan, the founder of social media monitor LikeFolio, told CNBC in an interview on Monday. Swan said he's not sure United ever "bounces back" from public relations nightmares like this — because it's really "nothing new."

This is likely the reason why United Continental's stock hardly reacted negatively to Sunday's debacle, with shares actually up about 1 percent by Monday afternoon, Swan added.

As he monitored social media sites like Facebook and Twitter to see how the public was responding to the video of a passenger being dragged, Swan said: "You see very negative reactions, lots of negative tweets about the brand. But the thing to remember is on airlines' [stock] it almost never matters."

Unless it's a real safety issue that blows up — like when the roof tore off a Southwest Airlines (LUV) plane in 2011 — most companies don't see changes in consumer purchasing behavior based on these types of events, Swan told CNBC. And that's what Wall Street is concerned about — ticket sales and seats filled.

At the end of the day, bad brand image or not, many people are going to continue to buy their airline tickets based on metrics like the lowest price or the best arrival time, social media expert Swan said. It's not like Chipotle (CMG), for example, which has to fight to win back customers after its E. coli fiasco.

"Tomorrow we'll be talking about something else," Swan laughed.

CORRECTION: This story's headline has been updated to say a United passenger was being immature, according to former Continental CEO Bethune's interview on CNBC.

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