How airlines decide when to kick a passenger off a plane

Los Angeles Times 

Two women were removed from a JetBlue Airways plane for reportedly staring at a flight attendant. The leader of a popular rock band was kicked off a Southwest Airlines flight for refusing to pull up his baggy pants. A UC Berkeley student said he was booted from a Southwest flight for speaking Arabic. Examples of passengers being removed from flights have gained increased attention since the Sept. 11, 2001, terrorist attacks, which began with the hijacking of four commercial planes. After the attacks, flight personnel suddenly found themselves focusing more attention on identifying potentially dangerous passengers than serving drinks and snacks.