The International Airport Irkutsk is located 8 km away from the city center and 60 km away from Lake Baikal. The airport has direct international and domestic flights from/to about 74 cities. Please check out the official website for detailed flight schedules.
There is a regular train service to the countries in Europe and Asia:
Train tickets can be purchased on the official website or RussianRailways.com of Russian Railways.