Justin Bieber is once again defending himself against being a brat. The singer reportedly acted out on a flight after a fellow passenger reportedly accused the pop star of giving the staff a hard time before take-off. According to Fox411.com, Bieber reportedly refused to take his seat before his flight from Los Angeles to Asia took off. A source said, “He gave the staff a really hard time the whole flight, nobody could believe it. And then at the end, the captain introduced himself to Justin and kindly asked for an autograph, and he rudely refused. “However, according to TMZ, Justin has no idea why anyone would say that. He said, “I have no clue. I have never heard that rumor. I don’t think you should believe everything you hear. People make up stuff all the time.” Bieber was recently accused of being a brat by his CSI: Cime Scene Investigation cast member Marg Helgenberger.