The basics
Flying from the US to Europe means heading east, and eastbound jet lag is harder than westbound. Whether you're crossing 5 time zones (New York to London) or 9 (Los Angeles to Paris), you're asking your body to fall asleep earlier and wake earlier than it wants to. That goes against your body's natural rhythm, which runs slightly longer than 24 hours.
Most US to Europe flights are red-eyes: you depart in the evening and arrive the next morning. This means you land having had at most 3 to 4 hours of broken sleep, already a full day into sleep debt, with your clock set to an American timezone where it's still the middle of the night.
Recovery time depends on how many zones you've crossed. From the East Coast (5 hours), expect 3 to 5 days. From the West Coast (8 to 9 hours), expect 5 to 7 days.
What jet lag feels like on this route
The main symptom is an inability to fall asleep at local bedtime. You go to bed at 11pm London time feeling completely alert, because your body thinks it's 6pm (or 3pm if you've come from California). When sleep finally comes, often at 1 or 2am, it's deep but short. You wake groggy and spend the morning in a fog.
The afternoon usually brings a window of clarity, followed by an evening where you feel frustratingly awake again right when you should be winding down. This cycle repeats, improving slightly each day.
Recovery plan
You'll land in the morning. Do not go to your hotel and sleep. This is the single biggest mistake people make. Get outside into daylight. Walk, have breakfast at a café. Morning light is what pulls your clock forward. Eat lunch at local time. If you're falling apart by 3pm, a 20-minute power nap is fine, but set an alarm. Push through to a 9 to 10pm bedtime. Take melatonin (0.5 to 1mg) 30 minutes before.
On days one and two, force yourself up by 7 to 8am. Morning light exposure, every day. The evening insomnia will persist but improve. You might fall asleep by midnight on day one, 11:30pm on day two. Keep taking melatonin at your target bedtime.
By days three and four, East Coast arrivals are usually adjusted. Sleep should feel close to normal.
West Coast arrivals need longer. The larger shift just takes more time. Keep the routine: morning light, evening melatonin, consistent wake time. By day five or six, most people are sleeping normally.
What helps
Get outside before 10am every morning for at least 30 minutes. This is the most effective intervention for eastbound jet lag.
Avoid bright light in the evening. Screen filters, dim lighting, and avoiding brightly lit environments after 8pm all help signal that the day is ending.
Melatonin at destination bedtime, low dose (0.5 to 1mg). Higher doses cause next-day grogginess without speeding up adjustment.
Eat at local mealtimes. Your gut clock is a secondary synchroniser, and keeping it on local time helps the main clock follow.
What to avoid
Don't take a "quick nap" at 10am that turns into a three-hour sleep. Set an alarm for any nap.
Don't stay up until 3am because "I'm not tired yet." You need to be in bed in the dark at your target bedtime, even if sleep doesn't come immediately. The darkness itself is a signal.
Don't drink espresso at 8pm because you're flagging. You'll be awake until 2am.