Are there nonstop flights from Seoul (ICN) to Jeju City (CJU)?

Yes. Jeju Air fly this route. Flight time is about 1h 1m.

What is the fastest connection from Seoul (ICN) to Jeju City (CJU)?

via Daegu ≈ 1h 42m, via Busan ≈ 1h 45m, via Fukuoka ≈ 2h 6m (estimated flying time, excluding layovers).

from 12,000 JAL miles (economy, one way, based on the published award charts).

Incheon International Airport (ICN) to Jeju International Airport (CJU)・440 km

Nonstop flights available (1 airline). Flight time about 1h 1m. Nonstop return flights also operate.

With milesJAL 12,000 miles+ (via TAE)Economy, one way, estimate. Tap a connection for miles by cabin.

6 one-stop options, sorted by estimated flying time. Tap one to see the airlines on each leg and booking links.

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