MOSCOW: The Russian Defence Ministry said on Saturday it had sent a fighter plane on  Friday to intercept a US aircraft approaching its border over the  Baltic Sea because the American plane had turned off its transponder,  which is needed for identification. The Pentagon said the US Air Force  RC-135 plane had been flying a routine route in international airspace  and that the Russian SU-27 fighter had intercepted it in an “unsafe and  unprofessional” way. CNN reported that the Russian jet had come within  about 100 feet of the US plane and had performed a barrel roll. “All  flights of Russian planes are conducted in accordance with international  regulations on the use of airspace,” the Russian Defence Ministry said  in a statement.