The Tu-134 jet slammed into a highway just before it was to land at Petrozavodsk airport on June 20.
Forty-seven people died in the crash. There were five survivors.
The spokesman did not say whether the navigator was at the controls at the time of the crash. He also did not specify the level of intoxication.
Officials said there appeared to be a number of factors in the crash, including fog and poor communication among the crew during the landing attempt.
Russia and other former Soviet republics have had poor air safety records in recent years.
The Sept. 7 plane crash near Yaroslavl that killed 37 players, coaches and officials of a top Russian ice hockey team drew new attention to Russia's poor air safety.
The Associated Press contributed to this report.