More than a fifth of Federal Air Marshal Service's field offices will be closed over the next two years,according to NBC News. Bases in Pittsburgh, Tampa, Cleveland, Phoenix, San Diego and Cincinnati will be gone, leaving 20 sites across the country. The cities were chosen due to of changing airline priorities and mergers with flight patterns and passengers loads also being taken into consideration. However, air marshals will continue to fly in and out of the cities which are losing field offices. The highly trained flight officers protect passengers by neutralizing potential terror threats.