The best flights from Chicago to London

These overnight flights will be easier to sleep through. Your body clock will still be on your Chicago timezone, so getting to sleep will be easier for flights after 9pm. By the time dinner is cleared away, it will be about 11pm and you'll feel naturally tired.

The second big benefit is that the flights will land nearer a time you would typically wake up in Chicago. Your body will have had more chance to rest and recharge without interruption at a somewhat normal time. Earlier flights will leave you sleep deprived. Remember, you'll typically be offered breakfast 1-2 hours before landing too. That will feel easier nearer 6-7am on your body clock than 1-2 am.

If you do have to take an earlier flight, see if you can get the earliest possible flight then get home or to a hotel for a "proper" sleep until lunchtime in London the day you land (your body will want to this anyway). If you can land around dawn, get out the airport quickly, and beat the morning rush hour traffic home, this also works. Your flight then isn't so critical for sleep.

Studies show the effects of lower cabin altitude (more oxygen and humidity) help with feeling less fatigued when you land.

787s, A350s and A380s have lower cabin altitudes than other aircraft. On long flights, like from London to Chicago, you'll notice your skin, mouth, and nose dry through the flight.