Allegiant Airline has made its business from purchasing used regional jets and using them to transport passengers. The pilots employed by Allegiant claim that the company's older planes have mechanical issues and are unsafe. The airline prides itself on providing the safest flying experience, so a claim such as this could jeopardize business.
See "Pilots at Allegiant Air Question Safety Standards", Jad Mouawad, The New York Times, April 19, 2015