Justin Bieber's appeal doesn't come only from his good looks and sweet voice. He comes off as the likeable boy-next-door with a dream and a million-dollar smile.

But news has been spreading that the young singer is actually quite the diva. Fox News reported that on a flight from LA to Asia, Bieber was intolerable. A source claimed the commotion began when the flight staff asked him to sit down in preparation for takeoff.

"He then gave the staff a really hard time the whole flight; nobody could believe it," said the source. "And then at the end, the captain introduced himself to Justin and kindly asked for an autograph, and he rudely refused."

This isn't the first time Bieber has been accused of having a bad attitude. "CSI" actress Marg Helgenberger described Justin as "kind of a brat" to a French radio show where he had made a guest appearance. Helgenberger said he was nice to her during their scene, but not so kind to the crew. "He locked one of the producers in a closet," she said. "And he put his fist through a cake that was on the craft services table."

Not long after this incident, David Koch, the host of "Sunrise," an Australian morning show, said Bieber was unpleasant on the set for rehearsals. He even said that Bieber got angry and cursed at the floor manager when he was instructing the singer on where he needs to perform. "I thought, 'Maybe someone needs to drag you aside and give you a bit of a slap,'" Koch said.

Bieber has not been silent since these allegations. He tweeted: "hearing adults spread lies and rumors is part of the job I guess. But all I have to say is ... kill em with kindness. So everyone keeps smiling."

Beyond direct rudeness to behind-the-scenes professionals, Justin Bieber has been accused of ignoring fans and shoving photographers. He was even caught flipping off paparazzi.

Of course, no one may want to believe these horrible things about Bieber -- who, for the most part, has a squeaky clean image. He is largely known for going out of his way to greet fans humbly and being kind to everyone around him. He serves the public through charity, etc. However, if these stories are true, Bieber's actions are not considered unusual.

"The brain is not even fully developed until the age of around 25, and the last part of the brain to mature is the executive/decision-making center. Second, kids are naturally narcissistic. He really hasn't done anything that many 'bratty teenagers' in America don't do. They simply do not have the spotlight on them," said Dr. Nancy Irwin, an LA psychologist.

The 17-year-old singer shot up to fame and fortune extremely fast. His attitude and behavior is the outcome of being spoiled by all the people and fans around him. Everyone loves him, follows his every move, pays attention to his every thought on Twitter, and sells out his concerts in minutes. Who wouldn't have a big head at that point? But hope is still alive for Bieber to readjust his behavior.

"I do think it is possible to keep Justin grounded in show business, although it requires the delicate balance of encouragement and validation, and a reminder that he is still human with flaws and imperfections. Justin really needs to be surrounded by childhood friends who will still treat him as one of the gang instead of God," said Dr. Patrick Wanis, a behavioral expert.