Flight time & jet lag: London to Chicago

London to Chicago: Route overview

This westbound transatlantic route covers 6,345 km from London to Chicago, crossing the Atlantic with prevailing westerly headwinds that typically extend the 7h 33m to 8h 34m journey by 20–40 minutes compared to the eastbound return. Crossing 6 time zones westbound creates significant circadian disruption. Your body's internal clock will take approximately 4 days to fully realign with Chicago's local schedule. Both cities sit at similar temperate latitudes, meaning daylight patterns will feel familiar upon arrival — a helpful factor for circadian adjustment.

What makes the London–Chicago route different

While westbound travel is generally easier than eastbound (your day gets longer rather than shorter), crossing 6 time zones still creates substantial disruption. The advantage is that most people find it easier to stay awake past their usual bedtime than to fall asleep earlier.

Arrival strategy for Chicago

Flying west to Chicago gains you 6 hours, extending your arrival day. At 18:00 local time, your body will think it is 00:00 — meaning you will feel ready for sleep well before the local bedtime. Counter this by getting bright light in the late afternoon and early evening. Eat dinner at the local time, stay physically active, and push your bedtime to at least 21:00 local. Avoid morning light before 08:00 on the first few days, as this would advance your clock in the wrong direction.

Circadian rhythm analysis: London → Chicago

When you arrive in Chicago, your circadian rhythm is still running on London time. At 09:00 Chicago time, your body reads 15:00 — your body's mid-afternoon, meaning you will be alert and functional during the local morning. The main westbound challenge is that by 22:00 local, your body clock reads 04:00 — the deep night on your internal clock. You will feel intensely sleepy well before the local bedtime. Your circadian system adjusts at roughly 1 to 1.5 hours per day, so expect 4 days for full alignment.

Your body clock in Chicago (day 1)

How your body clock maps to local time upon arrival, before any adjustment.

Pre-departure preparation

For this 6-hour westward shift to Chicago, start 4 days before departure by delaying your bedtime by 90 minutes each night. Seek bright light in the evening hours to help push your clock later. On the flight, try to stay awake if arriving during Chicago's daytime. This gradual shift can significantly ease your transition upon arrival.

Your first 72 hours in Chicago

Day 1 in Chicago: Your body is ~6 hours off local time. Stay active and seek afternoon sunlight. Push bedtime to at least 21:00 local. Eat at local mealtimes even if not hungry. Caffeine is fine before 16:00, not after. Day 2: ~5 hours off. Continue late afternoon (15:00–18:00) light exposure. Sleep quality should improve. Day 3: ~3 hours off. Noticeable improvement. Maintain light and meal timing discipline.

Recovery timeline

Full circadian adjustment for the London → Chicago route typically takes 4 days, based on the body's natural adaptation rate of ~1 to 1.5 hours per day for westbound travel. During this period, expect gradually improving sleep quality, with the most noticeable symptoms (fatigue, difficulty concentrating, appetite changes) during the first 3 days. By day 4, most travelers report feeling fully synchronized with Chicago's schedule.

Route Planner

Adjust departure date for DST-accurate results.

Jet lag adjustment plan: London → Chicago

Significant jet lag. Allow 4–7 days for full adjustment. Plan sleep and light exposure carefully.

Business hours: London vs Chicago

Seasonal and climate factors

Transatlantic flight times between London and Chicago vary seasonally: winter jet streams can reduce eastbound flights by 30–45 minutes while extending westbound flights by a similar amount. Summer typically sees more moderate wind patterns. Chicago at 42°N experiences moderate seasonal daylight variation. Summer offers longer evenings useful for westward adjustment, while winter's earlier sunsets support eastward adjustment schedules.

How the London–Chicago flight time is estimated

The 7h 33m to 8h 34m estimate for London to Chicago is derived from the 6,345-km great-circle distance. Long-haul flights spend most of their duration at optimal cruise altitude (typically 35,000–40,000 feet), achieving effective speeds of 820–900 km/h. An additional 30–50 minutes accounts for taxi, takeoff, climb, descent, approach, and taxi at both LHR and ORD. This oceanic route means actual flight paths follow organized track systems that may deviate from the great-circle distance, potentially adding 5–10% to the theoretical minimum path. Prevailing winds along this corridor can shift the actual time by 20–60 minutes in either direction.

Wind patterns and flight duration

Westbound flights from London to Chicago fly against the North Atlantic jet stream, adding time compared to the eastbound leg. Airlines often route these flights on more southerly tracks to minimize headwind exposure, which increases the path distance but can still reduce total time.

Practical travel context

As a transatlantic connection between London and Chicago, this route is primarily served by full-service carriers with seasonal charter supplements. Direct flights typically use wide-body aircraft suited to the 6,345-km distance. For stays shorter than 6 days, some travelers opt not to fully adjust to local time. Instead, they maintain a compromise schedule between origin and destination time, which can be effective for brief business trips.

Frequently asked questions: London to Chicago

More questions about this route

Related routes