How turbulent is LAX-ICN typically?

Light to moderate. The strongest chop sits near the jet core, and crews plan cruise levels around it.

What is the best altitude to avoid turbulence on LAX-ICN?

Flying above the jet core, generally FL380-FL410, gives the smoothest ride. Below it the shear is stronger.

When is the best time of year to fly LAX-ICN?

Summer and early autumn, when the East Asian jet is at its weakest. Winter brings the strongest core winds.

What causes the turbulence on this route?

Shear at the boundary of the East Asian jet stream, the strongest sustained upper wind on the planet.

Turbulence forecast LAX → ICN. Los Angeles to Seoul Incheon. SkyBriefing.

Los Angeles to Seoul: what the LAX to ICN corridor looks like

Departure: Los Angeles International Airport, Los Angeles, the United States
Arrival: Incheon International Airport, Seoul, South Korea
Great-circle distance: 9,627 km (5,198 nm)
Typical airborne time: 11h 42m
Usual cruise levels: FL320 to FL410
Initial track: northwest bound

Route overview

The LAX to ICN sector connects Los Angeles International Airport in Los Angeles, the United States, with Incheon International Airport in Seoul, South Korea. Measured along the great circle the two airports are 9,627 km apart, roughly 5,198 nautical miles, which is close to 11h 42m in the air before winds and routing are taken into account. The initial track is northwest bound, and the middle of the route sits in subtropical latitudes.

Leaving Los Angeles

Los Angeles International sits on the Pacific shoreline with the San Gabriel Mountains inland. Departures climb over water into the marine layer, and Santa Ana conditions in autumn add downslope wind from the ranges. The great-circle track leaves LAX northwest bound, and the first waypoint band of the flight sits close to 34.8N 147.2W. On a sector of 11h 42m, the climb to cruise takes roughly the first twenty to twenty five minutes.

The East Asian jet stream

Along the way the track passes over the open Atlantic and the open Pacific. The midpoint of the LAX to ICN track lies near 35.7N 4.0E, about 4,814 km from Los Angeles, which is where the corridor spends its longest continuous stretch at cruise level. The East Asian jet stream dominates the winds along this track. Its core is narrow and its position moves day to day, which is why dispatchers replan the route each cycle. Clear air turbulence sits at the edges of that core, and the WAFS forecast shows where it is expected before the flight departs.

Cruise altitudes on this sector

Ultra long sectors begin cruise lower, often near FL320 because of the fuel load, and finish two or three step climbs higher, up to FL400 or FL410. Choice of level matters because turbulence is layered: a change of two or three thousand feet often puts the aircraft into calmer air, and that is one of the first adjustments a crew will request.

Arriving into Seoul

Descending into Incheon means coming down through the edge of the East Asian jet toward a cold coastal boundary layer. That combination gives the arrival its character in the winter half of the year. Descent normally begins around 36.6N 155.2E, roughly 2,407 km before ICN, and takes about half an hour from cruise level to touchdown.

Seasonal pattern

The East Asian jet stream peaks in winter and weakens through the summer, so late summer and early autumn sectors are usually the smoothest on this corridor.

Flying this route with less worry

It is worth remembering that turbulence of the kind found on the LAX to ICN track is uncomfortable and entirely within what the aircraft is built for. Wings are designed to flex, the flight is planned around the forecast, and the crew adjusts level or track when it helps. The live forecast above shows the current picture for this corridor so there are fewer surprises on the day.