MOSCOW (Reuters) -Russian President Vladimir Putin fired his transport minister on Monday, in an unexpected move that comes at a time of significant challenges for the transport sector as the war in Ukraine drags on for a fourth year. Russia's aviation sector is short of spare parts and Russian Railways, the country's largest employer, is grappling with soaring interest costs as high rates - needed to curb higher inflation exacerbated by the war - take their toll. Putin's decree gave no reason for the dismissal of Roman Starovoit after barely a year in the job.