Are there nonstop flights from Ust-Kut (UKX) to Irkutsk (IKT)?

Yes. UTair Aviation, IrAero fly this route. Flight time is about 1h 7m.

Ust-Kut → Irkutsk

Ust-Kut Airport (UKX) to Irkutsk International Airport (IKT)・518 km

Nonstop flights available (2 airlines). Flight time about 1h 7m. Nonstop return flights also operate.

Times are estimated from distance. Check schedules, frequency and availability with the airline or a booking site.